voyager plaque explained

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• “Exploration is in our nature.” - Carl Sagan

Jake Rosenthal • Jan 20, 2016

The Pioneer Plaque: Science as a Universal Language

In 1972, an attempt to contact extraterrestrial life was cast into space with the launch of the Pioneer 10 spacecraft. This space vehicle was designed to explore the environment of Jupiter, along with asteroids, solar winds, and cosmic rays. Among a succession of firsts achieved by the spacecraft, Pioneer 10 would attain enough velocity to escape the solar system. This tacked on yet another first: the possibility of the interception of a human machine by an extraterrestrial civilization, providing us the opportunity to make contact with life from another world.

The suggestion of a message on Pioneer 10 was brought to Dr. Carl Sagan mere months before launch—a staggeringly brief period in the timescale of the design and test of spacecraft. Sagan passed along the idea to NASA, and to his surprise, the suggestion was embraced and approved by every level of the hierarchy. At that, Sagan joined Professor Frank Drake of Cornell University and, Sagan’s then-wife, artist Linda Salzman Sagan, to craft this extraterrestrial message. How would this great undertaking be fulfilled? What would we say? What in our roughly five-thousand-year recorded history needs to be said to tell the universe who we are? And how would we say it?

Humans speak nearly seven thousand languages, some with multiple dialects. The countless other species on Earth communicate with innumerably more, nearly all of which we have, thus far, failed to understand. By extrapolation, it is presumable that an alien language is different than any language we have developed. Human languages are products of human minds, and thereby, can be understood by human minds, by means of human senses—sight, sound, touch. How could we begin to imagine an extraterrestrial language if we cannot imagine with what senses the beings communicate? They may not have vocal chords with which they produce sounds or ears with which they capture them. So we must rely on universally-understood concepts, and devise a communication method neither specific to location nor species nor world. Perhaps, the only similarity between our species is the universe in which we both live. Thus, the language we are most likely to share is the study of the universe itself: science. The result of this conclusion was the Pioneer Plaque.

The Pioneer Plaque is a physical, symbolic message affixed to the exterior of the Pioneer 10 spacecraft. At the core of this message is a fundamental concept that establishes a standard of distance and time, which, thereafter, is employed by the other components of the plaque. The design team postulated that hydrogen, being the most abundant element in the cosmos, would be one of the first elements to be studied by a civilization. With this in mind, they inscribed two hydrogen atoms at the top left of the plaque, each in a different energy state. When atoms of hydrogen change from one energy state to another—a process called the hyperfine transition—electromagnetic radiation is released. It is this wave that harbors the standard of measure used throughout the illustrations on the plaque. The wavelength (approximately 21 centimeters) serves as a spatial measurement, and the period (approximately .7 nanoseconds) serves as a measurement of time. The final detail of this schematic is a small tick between the atoms of hydrogen, assigning these values of distance and time to the binary number 1.

The most prominent figures on the plaque are those of two adult humans: a man and woman. The man bends his arm and displays an open palm—an international greeting, but one that, admittedly, may be meaningless to an extraterrestrial civilization. The woman hangs her arms by her sides and stands with her weight shifted rearward as to dispel any misunderstandings regarding a fixed body and limb position; we are mobile and flexible. Beside the illustrations of the humans is the binary number 8, inscribed between two ticks, indicating the height the woman. The civilization could then conclude that the woman is 8 units tall, the unit being the wavelength (21 centimeters) described by the hyperfine transition key; thus, the woman is 8 times 21 centimeters, or about 5.5 feet tall.

At the heart of the plaque is an array of lines and dashes—a cosmic address on the interstellar letter. In the center is our home star; the radial spokes signify the relative distances and directions to pulsars—rapidly rotating neutron stars that emit electromagnetic radiation at regular intervals. Accompanying each line is the period of the respective pulsar—once again, in binary. Not only does this map communicate position, but time as well—an epoch in the lifetime of the universe during which the message was sent. The rate of electromagnetic bursts from pulsars changes over time; thus, the period of the pulsars denoted on the plaque serves as a timestamp. It is presumed that a civilization that has developed radio astronomy will have the capability to comprehend the nature of pulsars. Given the information presented in the pulsar map, it is feasible that such a civilization could date back the message and triangulate our position. As further confirmation of our locale, our solar system’s planets (nine at the time) are depicted in the bottom margin of the plaque with their respective distances to the sun in binary. Supposedly, in the history of the Milky Way, only one star has ever fit the characteristics displayed on the plaque.

The last signal from the Pioneer 10 spacecraft was received on January 22, 2003; NASA reported that the power source had depleted. Although the spacecraft can no longer speak to us, it presses onward—it now speaks for us. As interstellar courier, it bears the accumulated voice of every human, transcribed in, perhaps, the only common language in all the cosmos. We are but cosmic toddlers just learning how to take our first steps into space, and just learning how to speak to the universe.

Since Pioneer 10 was directed neither to an exoplanet nor a star, contact is extremely unlikely. But if, by the merest happenstance, the spacecraft is intercepted by an alien species, there is at least a chance that the species can interpret our message. In all likelihood however, Pioneer 10 and its plaque will be lost in the immense tranquility of empty space. But in no case was our attempt for naught. Pioneer 10 remains more than just a ghost of a ship, and the plaque is more than a shout into the void. The message we sent to the universe still echoes in our ears. Born from such a mission—one that spans space, time, and perhaps, civilizations—is a new mindset, an otherworldly perspective.

From the vantage of a distant world, our sun will be just another star, and our planet hidden in the radiance of the stellar glow. On such a world—one so distant and different from our own—we have not the slightest indication of what life will be like, how it began, how it evolved. If beings were to emerge, we know not their anatomy nor biology nor psychology, their physical traits, their sensory capabilities, their intellectual sophistication, their disposition; more or less, we are blind to every aspect of their species. They could be different in every way—in ways we have yet to understand or could even imagine. We make numerous assumptions about what life is and what life is not—educated guesses based off a sample size of one. But if, in some form or another, advanced consciousness arises elsewhere in the cosmos, it is possible that those beings will wonder, as we did: What are the lights in the sky? Where did the planets come from? What else is out there? Who else is out there? They may compile a system of knowledge of the cosmos and the laws that govern it; we call this “science.” About this hypothetical species, we know but one thing: the science they develop—the natural laws they discover—if they were to do so, would be exactly the same as our own.

Although not every human conducts science, it is conducted for every human. Science speaks to all of us in a way nothing ever has. It sparks new ideas and alternate perspectives. It brings each of us together and all of us forward. It is, at the very least, an international language, because there is an implied assertion with every question: there is something we do not know; and with our missions, we learn together. We probe the unknown looking for answers, venturing to understand the universe as it is—not the way we want it or believe it to be. Every step of the way, we strive not to fit the universe to the limits of our minds, but stretch our minds to the limitlessness of the universe.  

For every great scientific discovery and technological advancement, there was a time before, when the universe was a little less known. The significance and brilliance of our technologies and the science that drives them is too often overlooked. We forget the time before—a time without cell phones and personal computers, automobiles and airplanes—during which we wondered what it would be like to communicate at the speed of light and fly around to the other side of the planet in a matter of hours. Right now, at this time, we wonder what it would be like to find life elsewhere in the cosmos and to make first contact. This is the time before that great discovery, and there will be a time after. Maybe in the near future, or maybe a more distant one, it will be commonplace to carry on conversations with extraterrestrials; and again, we will forget how, right now, we are ceaselessly wondering, in endless search for an answer.

A Message from Earth , by Carl Sagan, Linda Salzman Sagan, and Frank Drake

The Cosmic Connection , by Carl Sagan

PIONEER 10 SPACECRAFT SENDS LAST SIGNAL , by Michael Mewhinney

Let’s Go Beyond The Horizon

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So, You’re Lost in Space: How to Read the Pioneer Plaque

• December 4, 2020

From out of space…a postcard?

This week, begin to decipher the cryptic symbols engraved on the face of the plaque which accompanies Pioneer 10 out of the familiar solar system and into undiscovered space

History and Composition

In 1973, one year after it was launched on February 27, 1972, the Pioneer 10 spacecraft became the first manmade object to leave the Earth’s solar system. The spacecraft was created to study Jupiter where the spacecraft would then use the immense momentum created by the gas giant to propel itself out of the solar system. Pioneer 10 is a small spacecraft, measuring in at 2.9 meters (9.5 feet) tall, only slightly taller than any unfortunate chrononaut that may find it floating in interstellar space, and it is relatively light at 258 kilograms (570 pounds). Since 1972, the spacecraft has trekked faithfully through the empty expanse of space towards the star Aldebaran—the eye of Taurus—about 65 light years away from Earth, powered by four radioisotope thermoelectric generators. While it is traveling around 11.5 km/second (about 25,700 mph) Pioneer 10 will take more than 2 million years to reach the celestial neighbor. Intended as a scientific instrument, it was known during its construction that Pioneer 10 would become the first manmade object to leave the familiar solar system for destinations unknown. In a spark of inspiration, it was agreed that in the unlikely chance it would be discovered by intelligent life, the spacecraft would be equipped with a simple greeting card from humanity. The engraving was designed in 3 short weeks by Carl Sagan, Frank Drake (of Drake Equation fame), and Linda Salzman Sagan. The 6-inch-by-9-inch (15.24 by 22.86 cm) plate is mounted externally on the antenna support structure, behind the ARC plasma experimental package. The Pioneer Plaque is 0.05 inches thick made of 6061 T6 gold-anodized aluminum plate, intended to be durable enough to endure the rough interstellar voyage. The message on the plaque is etched ~10 -2 cm deep, so the symbols would remain readable even after the accumulated damage barrage of micrometeorites over the travel distance of ~10 parsecs* (32.6156 light years), and possibly as far as 100 parsecs (326.156 light years)

Hyperfine Transition of Hydrogen

To begin deciphering the Pioneer Plaque, the top left diagram is the most important as it represents the legend and “universal yardstick” that will be used throughout the diagram. Rather than any specific language, the Pioneer Plaque uses mathematics as a universal language. It could be assumed that any technologically-advanced intelligence capable of catching the spacecraft would also be familiar with some common scientific features in space, most importantly, the characteristics of hydrogen, as it is the most abundant element in the universe. The two circles represent the same hydrogen atom in different states. This symbol represents the 21-cm hyperfine transition of neutral atomic hydrogen. 

The hyperfine transition in neutral hydrogen atoms occurs when the atoms change energy states and electromagnetic radiation energy is released at a precise wavelength. The transition of these states is represented by the inverted symbols on the top of circles displaying the antiparallel to parallel nuclear and electronic spins. As a wavelength, the change in energy states can represent two potential values: a unit of length (21 cm) or a unit of time (1450 hz). This creates a legend for the hydrogen-based cipher that is used throughout the diagram. The transition between each state is connected by a line in the diagram with the binary digit for 1 below to represent this transition as a binary value. The binary values used throughout the diagram represent either the length of time value of the hydrogen cipher

Binary Translation

Binary was chosen as an interstellar language on the plaque since it is the simplest representation of numbers and can survive long periods of time under the predicted erosion caused by micrometeorites in its path along the interstellar journey. 

Binary is a base two system, where a value can either be 0 or 1. It is read from left to right, where the position of the value (n) represents the value 2 n . The values for each position are multiplied by 2 n and finally added together to get the final value. For example, the binary value below is 100111 represents the integer value 39:

Each string of binary values on the diagram can be assumed to be read in either direction, making the true translation slightly obscured at first glance. However, since the string of binary values are displayed in the order of most significant digits, they all start with 1 and end in 1 or 0.

For example, on the far right center of the diagram, next to the women’s figure is the value either 0001 or 1000 in binary. Since the string must start with 1, the most significant digit, the value in binary is ‘1000’ representing the integer value of 8. 

Once translated from binary to an integer value, the value is translated to its intended length value by multiplying it by the hyperfine transition of hydrogen value of 21-cm. 

8 (in binary) x 21 (cm) = 168 (cm)

The value is intended to represent the average height of women at around 168 cm (or about 5-foot-6 inches)

Solar System Diagram

The bottom diagram represents the Earth’s solar system and is perhaps the most recognizable diagram for any terrestrial travelers. The nine planets (and the Sun) present at the time of the Pioneer’s launch are represented from left to right: the Sun, Mercury, Venus, the weary and familiar sight of Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

While each planet’s size and distance between each other is not to scale, they are accompanied by additional binary values that represent their relative distance from the Sun. These binary symbols are different from the binary values used throughout the plaque since they do not use the hydrogen cipher. This difference is indicated by the binary values being displayed as serif letters instead of sans-serif. After it has been translated from binary, the values represent a multiple of 1/10th the semimajor axis of the orbit of Mercury or 0.0387 A.U: 

integer value from binary X 0.0387 (AU) = orbital distance from the Sun

These values on the diagram would be difficult to resolve without knowing the orbit of Mercury. However, even if the distances of the solar system’s planet cannot be deciphered by an alien life, the representation of the rings of Saturn should help to distinguish the Earth’s solar system from the remaining thousands of the nearest stars that the pulsars could indicate. In addition, the small schematic of the Pioneer spacecraft indicates which planet in the diagram the craft was launched from as well the path it took around Jupiter and out of the solar system. The antenna is also positioned to point back at Earth to further clarify its point of origin.

With the combination of the 10 visible fingers and toes on each human and the use of the binary value of 10 to represent the orbit of Mercury it is also possible that this could be correctly interpreted as an indication of the Earth’s development of a base-10 counting system

How to Read a Pulsar Map with the Galactic Center

The most prominent and cryptic symbols of the plaque are the radial display on the left. This represents a display of stellar landmarks that give the position and frequency of 14 pulsars relative to the center of the map’s home star, the Earth’s Sun. Pulsars are rotating neutron stars that emit strong directional jets of high energy particles. Since the stream of electromagnetic radiation can only be observed when it is pointed in the direction of the observer, as the star rotates it acts much like a cosmic lighthouse. Pulsars can be identified by their unique and predictable rotational period.

Frank Drake identified the 14 pulsars with short periods of rotation and the greatest longevity and luminosity to make them easy to identify even after long stretches of time to serve as the prominent landmarks. The pulsars are displayed on the plaque as an axial radial map with the Earth’s Sun at the center, connected by 15 solid lines that end in tick marks. Each of the 14 radial lines represent a unique pulsar’s relative distance from the Sun. The 15th line is the longest horizontal line and runs behind the diagrams of the man and woman. This line has no binary representation and represents the galactic plane and the distance the Sun sits from the center of the galaxy. This is a reference line for all the other pulsar’s distances. The length of a pulsar’s line can be compared to the length of the 15th line to gauge their relative distances compared to the distance between the Sun and the center of the galaxy. 

If the Pioneer craft is intercepted within the next few tens of millions of years—even after it has travelled hundreds of parsecs—it is likely that all 14 pulsars will still be detectable. Even if they are not all as visible, only a few pulsars are needed to triangulate the Pioneer’s point of origin. In addition, two of the Pulsars (0950 and 1929) are particularly close to the Earth’s sun, allowing the position of the Earth to be approximated to within 1 in 103 stars.

The characteristic frequency of each pulsar is represented in binary along each axial line, however since the hydrogen cipher can represent both a distance and a time, there is no direct indication which is used for the pulsars. However, since the binary values are exceptionally large, they can be assumed to be a time, rather than distance, although a smart traveler (with ample time) could try both.

integer value from binary x 1450 (hz) = Period (in units of hyperfine transition of Hydrogen)

Along the axial spokes, the string of binary numbers represent the unique frequency of the pulsar at the time of the Pioneer launch. Pulsars radiate at a regular frequency emitting electromagnetic radiation at predictable intervals and over time that frequency decreases, allowing the exact period of the pulsar to serve as a timestamp. The pulsars allow an intelligent civilization with historical records of pulsars to determine the time elapsed since the Pioneer was launched, acting as a landmark of time and space.

The tick marks near the end of each axial spoke line represent the z-coordinate relative to the galactic plane. They are also used to determine the distance from the galactic center for each pulsar. The angle between the line representing the galactic plane and the tick mark of a pulsar represents the direction angle from the galactic center. 

The distance each pulsar is shown on the pulsar map as a relative distance. The distance for each pulsar is from the center of the map to the tick mark on the line for each pulsar. The length of the 15th line for the galactic plane can be labelled as 100, so that when the length is compared to the distances for each pulsar they lie between 1 and 100.

While the map is a flat two-dimensional object, it can be extrapolated based on the polar coordinates (r, θ) of each pulsar. As a coordinate, r is the distance a pulsar is from the Sun and θ is the angle between the galactic plane and the tick mark on the end of the axial spoke. Pulsars above the horizontal line of the galactic plane are stars found above the Sun’s relative position in the galaxy (+) and those beneath it sit below the Sun along the galactic disc (-)

Human Diagrams

The plaque includes an artistic diagram of two humans to represent the starry-eyed creatures that created and launched the plaque and spacecraft. The figures, a man and a woman, were intended as a universal greeting and representatives of all mankind. 

Any meaning from the stances or features of the figures would likely be lost on any alien life, but among humans the man’s upraised hand is considered a universal symbol of goodwill and was included for want of a better symbol. However, it has the additional advantage of clearly displaying the human hand and the opposable thumb. With the ten visible fingers and toes, an optimistic writer could hope that this could potentially be a clue to humanity’s arboreal lineage and base-10 counting system. The woman stands in a different, more relaxed pose than the man, with her body weight shifted to display the flexible and mobile nature of the human body as well as the diversity among different human body types. Originally they were envisioned to be holding hands in a gesture of goodwill, but were eventually decided to be separated to avoid accidentally implying that they are a single organism. Both figures are positioned in front of a large schematic of the Pioneer spacecraft to put them in scale with the spacecraft. Whether or not the Pioneer Plaque will be discovered by alien life or curious and lost chrononauts, the plaque serves as a message to the universe from a time when humanity had first begun to take bold strides into the stars and beyond

Pioneer 10 was sent with an intergalactic return address, but no stamps

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Will the messages we sent to the stars be understood?

While we cannot take anything for granted when it comes to how these messages might or might not be interpreted, let’s assume that the beings who might find the spacecraft can at least see or hear with eyes or ears similar to our own. Each message was designed with not only the information it was to carry in mind, but also the means to establish understanding through common denominators found throughout the universe.

The Pioneer plaque

Pioneer 10 and 11 each carry a 6 x 9-inch (15 x 23 centimeters), gold-anodized aluminum plaque. The plaque is affixed to support struts close to the spacecraft’s bus (main body). Carl Sagan and Frank Drake played key roles in designing the plaque and Linda Salzman Sagan, Sagan’s wife at the time, was the artist who actually drew the images engraved on the plaque.

The couple both have a bland expression (which may have been an attempt to avoid anything that could be interpreted as hostile) and the man is seen raising his right hand with the palm facing the viewer. While this gesture clearly conveys a greeting when viewed by another human, an extraterrestrial may have no way of interpreting this gesture. (Could you interpret a gesture made by an antelope … or a praying mantis?) It does show, however, that humans have opposable thumbs, as well as the general range of motion of the upper limbs.

With regards to the scientific data presented, the top left of the plaque shows the hyperfine transition of neutral hydrogen as a means of conveying to the reader baseline units of time (0.7 nanoseconds, the frequency of the transition) and distance (21 cm, the wavelength of the light released by the transition). If one is able to deduce that the image is that of hydrogen, the time and distance should be understandable.

The plaque also contains a map of our Sun relative to 14 pulsars as well as the center of our galaxy, conveying both the distances to the pulsars and their frequency in binary notation. As this image conveys copious objective data, a spacefaring species might well be able to easily interpret it.

Finally, the plaque contains a map of the solar system. The solar system map is likely among the more easily interpreted parts of the plaque, with Pioneer shown to have originated from the third planet. The plaque was created at a time when Pluto was still considered the ninth planet (before the discovery of other trans-Neptunian dwarf planets such as Eris and Sedna, among others), but it would still direct the reader’s attention to Earth if they were able to figure out that our solar system was the one depicted.

The Voyager record asks more of whoever finds it but gives more information in return. These phonographs, attached to the spacecraft bus, feature a cover illustration and over 90 minutes of audio on the reverse side. The cover illustration features the same image of hydrogen and the same pulsar map as found on the Pioneer plaque. Of critical importance, the Voyager records convey instructions on how to play them, such as how to affix the attached stylus, at what rate of rotation the record must be spun, and the proper waveform of signals generated by the record. It also explicitly tells the reader how to know if they are viewing the images properly via an engraving of what the first image (a circle) should look like. While this may seem very daunting, the challenge is primarily technical and might well be easily overcome by an advanced spacefaring species.

Similarly, the musical selections chosen demonstrate a wide range of human musical styles (ranging from works of Beethoven and Stravinsky to those of Chuck Berry, among others). While the lyrics of “Johnny B. Goode” are probably gibberish to an extraterrestrial, the beat and rhythm of the song would convey a tremendous amount to an alien listener.

Of perhaps the greatest importance are the 115 images encoded on the record . The first six images, if decoded properly, provide immense technical data for the reader regarding mathematical definitions, scales and sizes, as well as additional information regarding our location and how to find us. Images of the Sun and its spectrum, as well as some of the planets in our solar system, could help the discoverer of the Voyagers to find us should they decide to pay the Earth a visit. There are also approximately 20 medical and scientific diagrams including the structure of DNA and detailed images of human anatomy. These images could likely be interpreted correctly given their concrete nature.

The Voyager record also contains a plethora of images of humans engaged in a variety of activities (including eating, looking through a microscope, and even going on a spacewalk). While many of these images would be hard to interpret (e.g., a picture of a woman licking an ice cream cone or a photo of a string quartet) the images would at least convey that humans have created a complex civilization with some degree of advanced technology.

The Big Picture

As Marshall McLuhan famously said, “The medium is the message.” While the recipients of the Pioneer plaque or the Voyager record might never understand everything we are trying to convey, the fact that these messages were placed on interstellar spacecraft carry (both for them and for us) a deeper message — that humans created these spacecraft and that we want to tell the universe who we are.

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Pioneer 10: Greetings from Earth

Pioneer 10 was a breakthrough mission, accomplishing several firsts among spacecraft. It was the first to fly beyond Mars, the first to fly through the asteroid belt, first to swing by the planet Jupiter, and first to leave the solar system. Along the way, the spacecraft even generated a mystery of its own – the Pioneer Anomaly – that took decades for scientists to solve.

Thanks to Pioneer 10's pictures, the planet Jupiter and its moons , which were formerly only small circles in a telescope, became large, vibrant worlds in the eyes of scientists. For decades after those images beamed back to Earth, Pioneer 10 kept going. It sent valuable scientific data about the sun and cosmic rays before its signal became too faint for Earthlings to hear.

Pioneer 10 also carries a plaque with a message to any intelligent life it might encounter on its journey. The Pioneer plaque includes diagrams of Earth's location and drawings of a man and a woman.

Instruments and art

Launched on March 2, 1972, Pioneer 10 was the latest in a series of missions to explore space, which was still a very new frontier at the time. The earliest Pioneers aimed for the moon, while later generations forged farther and farther into space.

This spacecraft, powered by four radioisotope thermoelectric generators, measured 9.5 feet (2.9 meters) long and weighed 570 pounds (258 kilograms). Among the instruments and camera equipment on board, Pioneer also carried something special: a six- by nine-inch (15.2 by 22.8 centimeters) gold plaque.

The plaque depicts two nude figures – a man and a woman – along with diagrams of the solar system and the sun's position in space. It was intended to serve as a map to Earth for any extraterrestrials who might be curious about who made the spacecraft.

Two people designed the plaque: famed television host and astronomer Carl Sagan , and Frank Drake , founder of SETI and author of an equation that measures the likelihood of communicating with intelligent life.

Imaging Jupiter

Pioneer 10's primary target was the planet Jupiter . It launched from Earth on an Atlas-Centaur three-stage launcher, intended to boost the spacecraft to 32,400 mph (52,142 kph). Sailing away from Earth faster than any spacecraft before it, Pioneer soared by the moon just 11 hours later and made it past Mars in only three months.

Perhaps Pioneer's most dangerous phase was the asteroid belt between Mars and Jupiter, which it reached on July 15. Pioneer faced the risk of colliding with bits of asteroids, anywhere from the size of a small particle to rocks as big as the state of Alaska, according to NASA. But it made it safely to the other side and reached Jupiter on Dec. 3, 1973.

Pioneer 10 was just intended to be a scout for future missions, so its stay at Jupiter was brief. It came within 81,000 miles (130,000 kilometers) of the surface as it sailed past. Pictures beamed back to Earth revealed Jupiter as a liquid giant, while other instruments recorded information on Jupiter's radiation belts and magnetic fields.

The spacecraft also sent back snapshots of some of Jupiter's moons. Although the shots were taken from a distance, scientists could pick out shadows and featureson Europa , Ganymede , Io and Callisto . It was incredible resolution compared to the almost 400 years of observations previously done through telescopes.

On through the outer solar system

Pioneer's story does not end there. For about a quarter-century, the little spacecraft flew farther and farther away from Earth and continued producing science. It measured particles streaming from the sun, and cosmic rays incoming from outside the solar system.

Along with sister ship Pioneer 11, the spacecraft also embroiled scientists in an intergalactic mystery. For decades, NASA was puzzled as to why the two probes travelled 3,000 miles (4,828 km) less than projected, every single year.

Dubbed the "Pioneer Anomaly," it was only in 2012 that NASA found out what happened : heat flowing through the spacecrafts' power systems and instruments was pushing back on the Pioneers as they moved out of the solar system.

NASA concluded Pioneer's science mission on March 31, 1997, but kept track of the spacecraft through the Deep Space Network . Obtaining its signal was used as training for flight controllers looking to get data from the Lunar Prospector mission, which flew for 19 months before being deliberately crashed into the moon's surface in 1999 .

Pioneer 10 last sent data back to Earth on April 27, 2002. Its decaying signals were just too faint for NASA's antennas to pick up anymore.

As far as we know, the spacecraft sails on. NASA warmly refers to Pioneer 10 as a " ghost ship " of the outer solar system as the spacecraft coasts in the general direction of Aldebaran – the eye of the bull in the constellation Taurus.

Residents of that region of space will need to be patient if they want to see Pioneer 10. NASA expects it will take the spacecraft 2 million years to traverse the 68 light-years of space to Aldebaran.

— Elizabeth Howell, SPACE.com Contributor

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Voyager Golden Records 40 years later: Real audience was always here on Earth

Professor of Astronomy and Astrophysics, Penn State

Disclosure statement

Jason Wright acknowledges funding from NASA, the NSF, the Center for Exoplanets and Habitable Words at The Pennsylvania State University, and from Breakthrough Listen, part of the Breakthrough Initiatives sponsored by the Breakthrough Prize Foundation ( https://breakthroughinitiatives.org/ ).

Penn State provides funding as a founding partner of The Conversation US.

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Forty years ago, NASA launched Voyager I and II to explore the outer solar system. The twin spacecraft both visited Jupiter and Saturn; from there Voyager I explored the hazy moon Titan, while Voyager II became the first (and, to date, only) probe to explore Uranus and Neptune. Since they move too quickly and have too little propellant to stop themselves, both spacecraft are now on what NASA calls their Interstellar Mission , exploring the space between the stars as they head out into the galaxy.

Both craft carry Golden Records : 12-inch phonographic gold-plated copper records, along with needles and cartridges, all designed to last indefinitely in interstellar space. Inscribed on the records’ covers are instructions for their use and a sort of “map” designed to describe the Earth’s location in the galaxy in a way that extraterrestrials might understand.

The grooves of the records record both ordinary audio and 115 encoded images . A team led by astronomer Carl Sagan selected the contents, chosen to embody a message representative of all of humanity. They settled on elements such as audio greetings in 55 languages , the brain waves of “a young woman in love” (actually the project’s creative director Ann Druyan, days after falling in love with Carl Sagan ), a wide-ranging selection of musical excerpts from Blind Willie Johnson to honkyoku , technical drawings and images of people from around the world, including Saan Hunters, city traffic and a nursing mother and child.

Since we still have not detected any alien life, we cannot know to what degree the records would be properly interpreted. Researchers still debate what forms such messages should take . For instance, should they include a star map identifying Earth? Should we focus on ourselves, or all life on Earth? Should we present ourselves as we are, or as comics artist Jack Kirby would have had it, as “the exuberant, self-confident super visions with which we’ve clothed ourselves since time immemorial”?

But the records serve a broader purpose than spreading the word that we’re here on our blue marble. After all, given the vast distances between the stars, it’s not realistic to expect an answer to these messages within many human lifetimes. So why send them and does their content even matter? Referring to earlier, similar efforts with the Pioneer spacecraft , Carl Sagan wrote , “the greater significance of the Pioneer 10 plaque is not as a message to out there; it is as a message to back here.” The real audience of these kinds of messages is not ET, but humanity.

In this light, 40 years’ hindsight shows the experiment to be quite a success, as they continue to inspire research and reflection.

Only two years after the launch of these messages to the stars, “Star Trek: The Motion Picture” imagined the success of similar efforts by (the fictional) Voyager VI. Since then, there have been Ph.D. theses written on the records’ content , investigations into the identity of the person heard laughing and successful crowdfunded efforts to reissue the records themselves for home playback.

The choice to include music has inspired introspection on the nature of music as a human endeavor, and what it would (or even could) mean to an alien species. If an ET even has ears, it’s still far from clear whether it would or could appreciate rhythm, tones, vocal inflection, verbal language or even art of any kind. As music scholars Nelson and Polansky put it , “By imagining an Other listening, we reflect back upon ourselves, and open our selves and cultures to new musics and understandings, other possibilities, different worlds.”

The records also represent humanity’s deliberate effort to put artifacts among the stars. Unlike everything on Earth, which is subject to erosion and all but inevitable destruction (from the sun’s eventual demise, if nothing else), the Golden Records are essentially eternal, a permanent time capsule of humanity. And unlike the Voyager spacecraft themselves – which were designed to have finite lifespans and whose journey into interstellar space was incidental to their primary function of exploring the outer planets – the Golden Records’ only purpose is to serve as ambassadors of humanity to the stars.

Placing artifacts in interstellar space thus makes the galaxy subject to the social studies, in addition to astronomy. The Golden Records mark our claim to interstellar space as part of our cultural landscape and heritage , and once the Voyager spacecraft themselves are not functional any longer, they will become proper achaeological objects . They are, in a sense, how we as a species have planted our flag of exploration in space. Anthropologist Michael Oman-Reagan muses , “Has NASA been to interstellar space because this spacecraft has? Have we, as a human species, [now] been to interstellar space?”

I would argue we have, and we are a better species for it. Like the Pioneer plaques and the Arecibo Message before them, the Golden Records inspire us to broaden our minds about what it means to be human; what we value as humans; and about our place and role in the cosmos by having us imagine what we might, or might not, have in common with any alien species our Voyagers eventually encounter on their very long journeys.

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How Voyager Works

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At this moment, two spacecraft that were launched from Earth in 1977 hurtle through space at more than 30,000 mph (48,280 km/h). They are both several billion miles away, farther from Earth than any other man-made object. On Aug. 25, 2012, one of them crossed into interstellar space, making the first spacecraft to leave the solar system

Voyager 1 and 2 carry coded messages to potential alien civilizations. They have already taught scientists a great deal about the heliosheath , the outermost layer of the solar system. But none of this is even what they were designed for.

The Voyager spacecrafts were built to fly past the outer planets ( Jupiter , Saturn , Neptune and Uranus ) and study them closely, the first time in human history they'd been observed up close. The spacecraft succeeded magnificently, advancing planetary science by vast leaps. It was only after they’d accomplished their primary mission that they continued on to become Earth’s most far-ranging explorers.

Yet it was a matter of extremely good luck and timing that the missions were possible at all -- and an equal stroke of bad luck that almost scuttled the Voyager project before it ever left the ground. These ambitious missions were the product of new advances in the science and math of orbital trajectories, but they were almost cast by the wayside in favor of the expensive space shuttle program. Virtually every unmanned space mission undertaken today relies on knowledge and experience gained by the Voyagers.

We’ll take a close look at the ungainly Voyager space probes and all the technical equipment they carry on board. We’ll trace their trajectory from the development stages to their ultimate fate light years away from Earth. There will be stops at the largest planets in our solar system along the way. And if you’re wondering what's on the golden records each Voyager carries as messages for alien life forms, we’ll give them a spin. Will any aliens ever find them?

Voyager 1 and 2: The Grand Tour

Voyager equipment, to neptune and beyond, voyager golden record.

The 1970s were a transitional period for the U.S. space effort. The Apollo program was coming to a close, and NASA was trying to figure out what form manned spaceflight would take. The Mariner missions expanded our knowledge of the inner planets by sending space probes to fly past (and in some cases orbit) Mars , Venus and Mercury . There were tentative plans to send a Mariner mission to visit some of the outer planets, but using chemical rocket propulsion, such a trip would take 15 years or more.

At the same time, important advances were being made in the science of gravity-assisted orbital trajectories . While the math and physics involved are pretty complicated, the basic idea is that a spacecraft can use the gravity of a nearby planet to give it a large boost in velocity as long as the spacecraft follows the proper orbit. The higher the mass of the planet, the stronger the gravitational force, and the bigger the boost. That meant that once a space probe reached Jupiter (the most massive planet in our solar system ), it could use Jupiter’s gravity like a slingshot and head out to explore the more distant planets.

In 1965, an engineer named Gary Flandro noticed that in the mid-1970s, the outer planets would be aligned in such a way as to make it possible for a spacecraft to visit them all using a series of gravity-assisted boosts [source: Evans ]. This particular alignment wasn't just a once-in-a-lifetime event -- it wouldn't occur again for another 176 years. It was an amazing coincidence that the technical ability to accomplish such a mission was developed a few years before the planets lined up to allow it.

Initially, the ambitious project, known as the Grand Tour, would have sent a series of probes to visit all the outer planets. In 1972, however, budget projections for the project were approaching $900 million, and NASA was planning development of the space shuttle [source: Evans ]. With the immense shuttle development costs looming, the Grand Tour was cancelled and replaced with a more modest mission profile. This would be an extension of the Mariner program, referred to as the Mariner Jupiter-Saturn mission (MJS) . Based on the Mariner platform and improved with knowledge gained from Pioneer 10’s 1973 fly-by of Jupiter, the new probes eventually took the name Voyager. Design was completed in 1977. Optimistic NASA engineers thought they might be able to use gravity-assisted trajectories to reach Uranus and Neptune if the initial mission to visit Jupiter and Saturn (and some of their moons) was completed successfully. The idea of the Grand Tour flickered back to life.

The final Voyager mission plan looked like this: Two spacecraft (Voyager 1 and Voyager 2) would be launched a few weeks apart. Voyager 1 would fly past Jupiter and several of Jupiter’s moons from a relatively close distance, scanning and taking photos. Voyager 2 would also fly past Jupiter, but at a more conservative distance. If all went well, both probes would be catapulted toward Saturn by Jupiter’s gravity. Voyager 1 would then investigate Saturn, specifically the rings, as well as the moon Titan. At that point, Voyager 1’s trajectory would take it out of the solar system’s ecliptic (the plane of the planets’ orbits), away from all other planets, and eventually out of the solar system itself.

Meanwhile, Voyager 2 would visit Saturn and several of Saturn’s moons. If it was still functioning properly when that was completed, it would be boosted by Saturn’s gravity to visit Uranus and Neptune before also leaving the ecliptic and exiting the solar system. This was considered a long shot, but amazingly, everything worked as planned.

Next, what kind of hardware did the Voyagers carry into space?

Voyager 2 launched from Cape Canaveral, Fla., on board a Titan-Centaur rocket on Aug. 20, 1977. Voyager 1 launched on Sept. 5, 1977. Why is the numbering reversed? Once en route to the outer planets, Voyager 1 passed by Voyager 2 and reached Jupiter first. NASA thought the public would be confused if Voyager 2 started reporting back first, so the numbering doesn't follow the launch order.

Both Voyager spacecraft are identical. They don't have a sleek, aerodynamic design because there's no aerodynamic friction in space to worry about. Weighing 1,592 pounds (722 kilograms), they're made up of a main bus, a high-gain antenna, three booms that held scientific instruments and the power supply, and two other antennae.

The main bus is the body of the Voyager. It's a 10-sided box 5.9 feet (1.8 meters) across, and it contains some scientific instruments, electronics and a fuel tank for the rocket thrusters. The thrusters are used to reorient the craft as it moves through space.

Mounted on top of the main bus, the high-gain antenna is 12 feet (3.7 meters) across and looks like a satellite dish. This antenna is how the Voyagers receive commands from Earth and send the data they gather back. No matter where a Voyager spacecraft flies, the high-gain antenna always points toward Earth.

One of the booms extending off of the main bus carries Voyager’s radioisotope thermoelectric power supply . Pellets of plutonium dioxide release heat through natural decay. This heat is converted into electricity using a series of thermocouples. Although the power output isn't very strong, it powers the electronics and instruments on board the Voyagers for a very long time. Power isn't expected to deplete completely until 2020. The power supply was placed on a boom to keep the radiation from interfering with the other scientific instruments.

The other two booms carry a series of instruments. These include:

• Magnetometer
• Cosmic ray detector
• Plasma detector
• Photopolarimeter
• Infrared interferometer
• Spectrometer
• Ultraviolet spectrometer
• Low energy charged particle detector
• Plasma wave detector

[source: Evans, Dethloff & Schorn ]

Perhaps the most significant instruments on board the Voyagers, as far as the public is concerned, are the cameras. Also mounted on the instrument boom, the cameras have a resolution of 800x800, with both wide-angle and narrow-field versions. The cameras returned unprecedented photos of the outer planets and gave us views of our solar system that we had never before witnessed (including the famous departure shot showing both Earth and Earth’s moon in the same frame). The boom carrying the cameras could be moved independently from the rest of the craft.

The Voyager’s computer system was very impressive as well. Knowing the craft would be on its own much of the time, with the lag between command and response from Earth growing longer the farther the craft went into space, engineers developed a self-repairing computer system . The computer has multiple modules that compare the data they receive and the output instructions they decide on. If one module differs from the others, it's assumed to be faulty and is eliminated from the system, replaced by one of the backup modules. It was tested shortly after launch, when a delay in boom deployment was misread as a malfunction. The problem was corrected successfully.

In the next section, we’ll find out what we learned from the Voyager missions.

While the Voyagers themselves did all the data gathering, there were important mission elements on the ground as well. The Voyagers’ signals became increasingly difficult to detect as they flew out into the outer solar system, so NASA improved a worldwide network of radio receiving stations to better detect them. A series of 230-foot (70-meter) radio dishes pull in the Voyager data and send signals out to it, maintaining almost continuous communication [source: Evans ].

Although the lifetime mission cost for Voyager exceeded $750 million, by 1989 the spacecrafts had returned enough scientific data to fill 6,000 editions of the Encyclopedia Britannica [source: Evans ]. The science modules on board were chosen from proposals submitted by research teams across the United States. The information about Jupiter , Saturn , Uranus and Neptune (and many of their moons) that we learned from the Voyager missions wasn't just vast in quantity, but also in influence. It shaped science textbooks in schools across the U.S., informed public perceptions of the solar system and laid the foundation for the modern space program. Much of what we know about the outer planets came from Voyager. That’s not to mention the thousands of photographs taken from vantage points humans had never experienced before. Those brilliant images of Jupiter and Saturn fired the public’s imagination and fueled enthusiasm for future space exploration.

From Voyager, we learned more about the weather on Jupiter; the rings around Jupiter, Saturn and Uranus; volcanic activity on Jupiter's moon Io; the masses and densities of Saturn’s moons; the atmospheric pressure on Titan, Saturn's largest moon; the magnetic field of Uranus; and a persistent weather system on Neptune as large as Earth , known as the Great Dark Spot . By the time Voyager 2 reached Neptune, it was 1989. More than 10 years had passed since launch, and many of the scientists working on the original mission had moved on. Voyager had passed by Jupiter, Saturn and Uranus in 1979, 1981 and 1986, respectively.

So where are they now? The two Voyagers aren't together. Voyager 1 is moving north (relative to the orientation of Earth out of the solar system), while Voyager 2 is moving south. In 2007, they both entered the heliosheath, the outermost section of the solar system. There, the solar wind meets interstellar magnetic fields and forms a boundary with a shock wave. The Voyagers traversed the shock wave and sent data back, giving astronomers their first idea of the shape and location of the heliosheath. On Sept. 21, 2013, Voyager scientists reported that Voyager 1 left the solar system on Aug. 25, 2012.

Although some instruments on the Voyagers are no longer working, they do continue to send back important information. Imagine a car that has been on the road continuously since 1977, and you'll get some idea of how amazing these spacecraft are. At their current distance, it takes radio signals traveling at the speed of light more than 14 hours to reach Earth. The craft are running low on fuel for their orienting thrusters and will have to power down some instruments in the coming years as their plutonium runs out as well. By 2020, they will be dark and silent.

Yet they will continue on their current trajectory, moving over 30,000 mph (48,280 km/h), arcing out into the Milky Way for tens of thousands of years. With no atmosphere in space, they will never corrode, and there is little for them to crash into in interstellar space. It will take them about 40,000 years before they even come within light years of another star . The Voyagers may be traveling for hundreds of thousands or even millions of years.

What if the Voyagers meet an intelligent alien civilization some day? We’ve left a message for them.

When NASA realized that the Voyagers would eventually travel beyond the edge of our solar system , they decided it might be a good idea to include some kind of message to any intelligent aliens who might some day find them. A committee headed by astronomer Carl Sagan put these messages together. They're contained on gold-plated copper discs, which are engraved much like a vinyl record album. A portion of the disc contains audio information, including a variety of music, greetings spoken in 55 different languages (including some that are very obscure or long extinct) and a selection of nature sounds. The discs also include 122 images, encoded as vibrations on the disc with instructions for decoding.

On each disc’s cover plate are several symbols that depict the method of playing back the record (a stylus and mounting platter are included as well). The image decoding instructions are revealed, describing the “image start” signal, the aspect ratio of the images, and a reproduction of the first image, so the aliens would know if they got it right. A star map clearly showing the location of Earth completes the picture.

If the aliens wonder how long the Voyager they find has been traveling, they can examine the piece of uranium-238 attached to the main bus near the record. Examining the isotope ratios (assuming they know the half-life of uranium-238), they could then deduce how long the sample had been in space.

What music will the aliens hear when they play the record? Mostly traditional music from a variety of cultures, such as Native Americans chants, Scottish bagpipes and African ritual music. It is also something of a “greatest hits” collection of classical music. The most contemporary songs are “Johnny B. Goode” by Chuck Berry and a jazz number by Louis Armstrong.

The images on the record are varied, and include maps of Earth, images of the other planets in our solar system, pictures of various animals and several images of humans. Carl Sagan wrote a book about the record, called "Murmurs of Earth." A companion CD-ROM was released decades later.

The Voyager discs are similar to a plaque that was placed aboard Pioneer 10 and Pioneer 11, although the creators of the Voyager discs spent a lot of time making sure the aliens could decode it. Many Earth scientists could not decode the information on the Pioneer plaque. At the time, some voiced concerns that any hostile aliens finding the Voyager disc would have a map leading them directly to Earth. However, the Voyagers will spend tens of thousands of years in interstellar space before they are anywhere near another star, so the matter isn’t really an immediate concern. If the discs are ever found, it may be so far in the future that humans no longer exist.

For more interesting articles about space exploration, try the next page.

In "Star Trek: The Motion Picture" (the first Star Trek film), much of the plot revolved around a strange electronic life form known as V’Ger. By the end of the film, it is revealed that V’Ger is one of the Voyager space probes (Voyager 6, which never existed in the real world) that has either gained sentience on its own or been given sentience by an alien race. It wants to eradicate all of humanity, but instead evolves into yet another form of life.

Within the fictional Star Trek universe, there is some dispute as to V’Ger’s place in Trek history. Some suggest that V’Ger created the Borg, a cold, logical alien race that would become the primary villains in "Star Trek: The Next Generation." Others think the Borg encountered V’Ger, but that the cyborg aliens existed before the chance meeting.

Voyager Space FAQ

What is the temperature of interstellar space, how far away is voyager 2, how far away is voyager 1, do the voyagers have a camera, what is the difference between voyager 1 and 2, lots more information, related articles.

• Are we not the only Earth out there?
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More Great Links

• Voyager Web site
• Evans, Ben. "NASA's Voyager Missions: Exploring the Outer Solar System and Beyond." Springer; 1st ed 2004. 2nd printing edition (April 15, 2008).
• Dethloff, Henry C & Schorn, Ronald A. "Voyager's Grand Tour: To the Outer Planets and Beyond." Smithsonian (March 17, 2003).
• NASA. “Voyager 2 Proves Solar System Is Squashed.” http://voyager.jpl.nasa.gov/

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The National Air and Space Museum's full-scale mockup of the Pioneer 10 spacecraft was recently moved to its new location in the Boeing Milestones of Flight Hall as a part of a major renovation to the gallery. The spacecraft includes power supplies, a large dish antenna, and several science instruments used during encounters with the outer planets of the solar system. It also contains something that might sound more like science fiction: A note to any alien civilization that might come across the spacecraft in the distant future.

A replica of the Pioneer 10 spacecraft on display in the Boeing Milestones of Flight Hall  at the Museum in Washington, DC.

Pioneer 10 and 11 were the first spacecraft designed to visit the outer solar system—the region beyond Mars. Designed as identical spacecraft, Pioneer 10 was launched on March 2, 1972, and Pioneer 11 on April 6, 1973. Both traversed the asteroid belt and visited Jupiter, while Pioneer 11 also visited Saturn on its way out of the solar system. Pioneer 10 and 11 returned data until 2002 and 1995, respectively, until their power supplies became too weak to support operations. Pioneer 10 and 11, although no longer functioning, are leaving the solar system at 2.6 and 2.5 AU per year, respectively. One AU is the mean distance from the Earth to the Sun, or approximately 150 million km (93 million miles). During planning stages of the Pioneer 10 and 11 missions, science writer Eric Burgess suggested adding a greeting to an alien civilization. The mission team eventually decided to add a small plaque with the message. The plaques were designed by Carl Sagan and Frank Drake and drawn by Sagan's wife at the time, Linda Salzman Sagan. The gold-covered aluminum plaques were affixed to the antenna supports of the two spacecraft. They faced inward for protection from possible erosion caused by micrometeorite strikes. In the mockup on display in the Museum, the artwork faces outward. In Pioneer's new location in the Museum, visitors can get a view of the plaque from the balcony near the Albert Einstein Planetarium box office on the second floor. Look between the large dish antenna and the main part of the spacecraft closer to the wall. The rectangular plaque, about 23 x 15 centimeters (9 x 6 inches), can be seen behind the dish facing the floor away from the National Mall. You can also catch a glimpse standing on the first floor near the bottom of the escalators in front of the Museum store.

  Deciphering the Pioneer Plaque The Pioneer plaque contains drawings of two humans and our place in the galaxy. The spacecraft is drawn behind a human male and female for scale. The solar system appears along the lower edge. Each planet and Pluto is shown with a binary number indicating the average distance from the Sun. Distances are listed in units of 1/10th the Mercury distance. The diagram in the upper left shows atomic hydrogen, by far the most abundant element in the universe. It shows a hydrogen atom undergoing a shift in its electron energy level. This change emits electromagnetic radiation at a wavelength of 21 centimeters (8 inches), and is the most common such emission in the universe. This is used as a frequency and distance scale represented by the binary number 1. Converging lines in the left show the position of the Sun relative to 14 pulsars in the Milky Way and the center of the galaxy. Pulsars are very dense remnants of exploded giant stars, and they rotate at very stable frequencies. The frequency of each pulsar is listed in binary numerals relative to the frequency of hydrogen emission. The average human height, of approximately 168 centimeters (or 5 feet 6 inches), is listed on the right-hand side as the binary number 8 (1000, shown as  | - - - ), relative to the 21 centimeter (8 inch) wavelength of hydrogen emission. Leaving the Solar System Besides Pioneer 10 and 11, three other spacecraft have reached the Sun's escape velocity and are currently moving out into the stars: Voyager 1, Voyager 2, and New Horizons . The two Voyagers visited the gas giant planets of our solar system. A version of the Pioneer plaque also appears on a gold-covered phonograph record on each of the Voyager spacecraft. Although the Voyager spacecraft were launched five years after the Pioneers, they are traveling faster, and currently the Voyager 1 spacecraft is the most distant form the Earth. New Horizons just flew by Pluto and will continue through the Kuiper Belt. New Horizons contains several objects including a sample of the ashes of Clyde Tombaugh, the discoverer of Pluto . However, it does not carry any material intended to greet alien civilization.

It is very unlikely that the Pioneers or any of the other spacecraft will ever been seen by any alien civilization, even very far into future. Despite this, four of the outgoing spacecraft contain messages. We can see them more as messages to ourselves, not to aliens. They remind us that in the mid-20 th Century A.D., human beings took the first steps toward exploring the universe.

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The most distant human-made object

No spacecraft has gone farther than NASA's Voyager 1. Launched in 1977 to fly by Jupiter and Saturn, Voyager 1 crossed into interstellar space in August 2012 and continues to collect data.

Mission Type

What is Voyager 1?

Voyager 1 has been exploring our solar system for more than 45 years. The probe is now in interstellar space, the region outside the heliopause, or the bubble of energetic particles and magnetic fields from the Sun.

• Voyager 1 was the first spacecraft to cross the heliosphere, the boundary where the influences outside our solar system are stronger than those from our Sun.
• Voyager 1 is the first human-made object to venture into interstellar space.
• Voyager 1 discovered a thin ring around Jupiter and two new Jovian moons: Thebe and Metis.
• At Saturn, Voyager 1 found five new moons and a new ring called the G-ring.

In Depth: Voyager 1

Voyager 1 was launched after Voyager 2, but because of a faster route, it exited the asteroid belt earlier than its twin, having overtaken Voyager 2 on Dec. 15, 1977.

Voyager 1 at Jupiter

Voyager 1 began its Jovian imaging mission in April 1978 at a range of 165 million miles (265 million km) from the planet. Images sent back by January the following year indicated that Jupiter’s atmosphere was more turbulent than during the Pioneer flybys in 1973–1974.

Beginning on January 30, Voyager 1 took a picture every 96 seconds for a span of 100 hours to generate a color timelapse movie to depict 10 rotations of Jupiter. On Feb. 10, 1979, the spacecraft crossed into the Jovian moon system and by early March, it had already discovered a thin (less than 30 kilometers thick) ring circling Jupiter.

Voyager 1’s closest encounter with Jupiter was at 12:05 UT on March 5, 1979 at a range of about 174,000 miles (280,000 km). It encountered several of Jupiter’s Moons, including Amalthea, Io, Europa, Ganymede, and Callisto, returning spectacular photos of their terrain, opening up completely new worlds for planetary scientists.

The most interesting find was on Io, where images showed a bizarre yellow, orange, and brown world with at least eight active volcanoes spewing material into space, making it one of the most (if not the most) geologically active planetary body in the solar system. The presence of active volcanoes suggested that the sulfur and oxygen in Jovian space may be a result of the volcanic plumes from Io which are rich in sulfur dioxide. The spacecraft also discovered two new moons, Thebe and Metis.

Voyager 1 at Saturn

Following the Jupiter encounter, Voyager 1 completed an initial course correction on April 9, 1979 in preparation for its meeting with Saturn. A second correction on Oct. 10, 1979 ensured that the spacecraft would not hit Saturn’s moon Titan.

Its flyby of the Saturn system in November 1979 was as spectacular as its previous encounter. Voyager 1 found five new moons, a ring system consisting of thousands of bands, wedge-shaped transient clouds of tiny particles in the B ring that scientists called “spokes,” a new ring (the “G-ring”), and “shepherding” satellites on either side of the F-ring—satellites that keep the rings well-defined.

During its flyby, the spacecraft photographed Saturn’s moons Titan, Mimas, Enceladus, Tethys, Dione, and Rhea. Based on incoming data, all the moons appeared to be composed largely of water ice. Perhaps the most interesting target was Titan, which Voyager 1 passed at 05:41 UT on November 12 at a range of 2,500 miles (4,000 km). Images showed a thick atmosphere that completely hid the surface. The spacecraft found that the moon’s atmosphere was composed of 90% nitrogen. Pressure ad temperature at the surface was 1.6 atmospheres and 356 °F (–180°C), respectively.

Atmospheric data suggested that Titan might be the first body in the solar system (apart from Earth) where liquid might exist on the surface. In addition, the presence of nitrogen, methane, and more complex hydrocarbons indicated that prebiotic chemical reactions might be possible on Titan.

Voyager 1’s closest approach to Saturn was at 23:46 UT on 12 Nov. 12, 1980 at a range of 78,000 miles(126,000 km).

Voyager 1’s ‘Family Portrait’ Image

Following the encounter with Saturn, Voyager 1 headed on a trajectory escaping the solar system at a speed of about 3.5 AU per year, 35° out of the ecliptic plane to the north, in the general direction of the Sun’s motion relative to nearby stars. Because of the specific requirements for the Titan flyby, the spacecraft was not directed to Uranus and Neptune.

The final images taken by the Voyagers comprised a mosaic of 64 images taken by Voyager 1 on Feb. 14, 1990 at a distance of 40 AU of the Sun and all the planets of the solar system (although Mercury and Mars did not appear, the former because it was too close to the Sun and the latter because Mars was on the same side of the Sun as Voyager 1 so only its dark side faced the cameras).

This was the so-called “pale blue dot” image made famous by Cornell University professor and Voyager science team member Carl Sagan (1934-1996). These were the last of a total of 67,000 images taken by the two spacecraft.

Voyager 1’s Interstellar Mission

All the planetary encounters finally over in 1989, the missions of Voyager 1 and 2 were declared part of the Voyager Interstellar Mission (VIM), which officially began on Jan. 1, 1990.

The goal was to extend NASA’s exploration of the solar system beyond the neighborhood of the outer planets to the outer limits of the Sun’s sphere of influence, and “possibly beyond.” Specific goals include collecting data on the transition between the heliosphere, the region of space dominated by the Sun’s magnetic field and solar field, and the interstellar medium.

On Feb. 17, 1998, Voyager 1 became the most distant human-made object in existence when, at a distance of 69.4 AU from the Sun when it “overtook” Pioneer 10.

On Dec. 16, 2004, Voyager scientists announced that Voyager 1 had reported high values for the intensity for the magnetic field at a distance of 94 AU, indicating that it had reached the termination shock and had now entered the heliosheath.

The spacecraft finally exited the heliosphere and began measuring the interstellar environment on Aug. 25, 2012, the first spacecraft to do so.

On Sept. 5, 2017, NASA marked the 40th anniversary of its launch, as it continues to communicate with NASA’s Deep Space Network and send data back from four still-functioning instruments—the cosmic ray telescope, the low-energy charged particles experiment, the magnetometer, and the plasma waves experiment.

The Golden Record

Each of the Voyagers contain a “message,” prepared by a team headed by Carl Sagan, in the form of a 12-inch (30 cm) diameter gold-plated copper disc for potential extraterrestrials who might find the spacecraft. Like the plaques on Pioneers 10 and 11, the record has inscribed symbols to show the location of Earth relative to several pulsars.

The records also contain instructions to play them using a cartridge and a needle, much like a vinyl record player. The audio on the disc includes greetings in 55 languages, 35 sounds from life on Earth (such as whale songs, laughter, etc.), 90 minutes of generally Western music including everything from Mozart and Bach to Chuck Berry and Blind Willie Johnson. It also includes 115 images of life on Earth and recorded greetings from then U.S. President Jimmy Carter (1924– ) and then-UN Secretary-General Kurt Waldheim (1918–2007).

By January 2024, Voyager 1 was about 136 AU (15 billion miles, or 20 billion kilometers) from Earth, the farthest object created by humans, and moving at a velocity of about 38,000 mph (17.0 kilometers/second) relative to the Sun.

National Space Science Data Center: Voyager 1

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How the Voyager Golden Record Was Made

By Timothy Ferris

We inhabit a small planet orbiting a medium-sized star about two-thirds of the way out from the center of the Milky Way galaxy—around where Track 2 on an LP record might begin. In cosmic terms, we are tiny: were the galaxy the size of a typical LP, the sun and all its planets would fit inside an atom’s width. Yet there is something in us so expansive that, four decades ago, we made a time capsule full of music and photographs from Earth and flung it out into the universe. Indeed, we made two of them.

The time capsules, really a pair of phonograph records, were launched aboard the twin Voyager space probes in August and September of 1977. The craft spent thirteen years reconnoitering the sun’s outer planets, beaming back valuable data and images of incomparable beauty . In 2012, Voyager 1 became the first human-made object to leave the solar system, sailing through the doldrums where the stream of charged particles from our sun stalls against those of interstellar space. Today, the probes are so distant that their radio signals, travelling at the speed of light, take more than fifteen hours to reach Earth. They arrive with a strength of under a millionth of a billionth of a watt, so weak that the three dish antennas of the Deep Space Network’s interplanetary tracking system (in California, Spain, and Australia) had to be enlarged to stay in touch with them.

If you perched on Voyager 1 now—which would be possible, if uncomfortable; the spidery craft is about the size and mass of a subcompact car—you’d have no sense of motion. The brightest star in sight would be our sun, a glowing point of light below Orion’s foot, with Earth a dim blue dot lost in its glare. Remain patiently onboard for millions of years, and you’d notice that the positions of a few relatively nearby stars were slowly changing, but that would be about it. You’d find, in short, that you were not so much flying to the stars as swimming among them.

The Voyagers’ scientific mission will end when their plutonium-238 thermoelectric power generators fail, around the year 2030. After that, the two craft will drift endlessly among the stars of our galaxy—unless someone or something encounters them someday. With this prospect in mind, each was fitted with a copy of what has come to be called the Golden Record. Etched in copper, plated with gold, and sealed in aluminum cases, the records are expected to remain intelligible for more than a billion years, making them the longest-lasting objects ever crafted by human hands. We don’t know enough about extraterrestrial life, if it even exists, to state with any confidence whether the records will ever be found. They were a gift, proffered without hope of return.

I became friends with Carl Sagan, the astronomer who oversaw the creation of the Golden Record, in 1972. He’d sometimes stop by my place in New York, a high-ceilinged West Side apartment perched up amid Norway maples like a tree house, and we’d listen to records. Lots of great music was being released in those days, and there was something fascinating about LP technology itself. A diamond danced along the undulations of a groove, vibrating an attached crystal, which generated a flow of electricity that was amplified and sent to the speakers. At no point in this process was it possible to say with assurance just how much information the record contained or how accurately a given stereo had translated it. The open-endedness of the medium seemed akin to the process of scientific exploration: there was always more to learn.

In the winter of 1976, Carl was visiting with me and my fiancée at the time, Ann Druyan, and asked whether we’d help him create a plaque or something of the sort for Voyager. We immediately agreed. Soon, he and one of his colleagues at Cornell, Frank Drake, had decided on a record. By the time NASA approved the idea, we had less than six months to put it together, so we had to move fast. Ann began gathering material for a sonic description of Earth’s history. Linda Salzman Sagan, Carl’s wife at the time, went to work recording samples of human voices speaking in many different languages. The space artist Jon Lomberg rounded up photographs, a method having been found to encode them into the record’s grooves. I produced the record, which meant overseeing the technical side of things. We all worked on selecting the music.

I sought to recruit John Lennon, of the Beatles, for the project, but tax considerations obliged him to leave the country. Lennon did help us, though, in two ways. First, he recommended that we use his engineer, Jimmy Iovine, who brought energy and expertise to the studio. (Jimmy later became famous as a rock and hip-hop producer and record-company executive.) Second, Lennon’s trick of etching little messages into the blank spaces between the takeout grooves at the ends of his records inspired me to do the same on Voyager. I wrote a dedication: “To the makers of music—all worlds, all times.”

To our surprise, those nine words created a problem at NASA . An agency compliance officer, charged with making sure each of the probes’ sixty-five thousand parts were up to spec, reported that while everything else checked out—the records’ size, weight, composition, and magnetic properties—there was nothing in the blueprints about an inscription. The records were rejected, and NASA prepared to substitute blank discs in their place. Only after Carl appealed to the NASA administrator, arguing that the inscription would be the sole example of human handwriting aboard, did we get a waiver permitting the records to fly.

In those days, we had to obtain physical copies of every recording we hoped to listen to or include. This wasn’t such a challenge for, say, mainstream American music, but we aimed to cast a wide net, incorporating selections from places as disparate as Australia, Azerbaijan, Bulgaria, China, Congo, Japan, the Navajo Nation, Peru, and the Solomon Islands. Ann found an LP containing the Indian raga “Jaat Kahan Ho” in a carton under a card table in the back of an appliance store. At one point, the folklorist Alan Lomax pulled a Russian recording, said to be the sole copy of “Chakrulo” in North America, from a stack of lacquer demos and sailed it across the room to me like a Frisbee. We’d comb through all this music individually, then meet and go over our nominees in long discussions stretching into the night. It was exhausting, involving, utterly delightful work.

“Bhairavi: Jaat Kahan Ho,” by Kesarbai Kerkar

In selecting Western classical music, we sacrificed a measure of diversity to include three compositions by J. S. Bach and two by Ludwig van Beethoven. To understand why we did this, imagine that the record were being studied by extraterrestrials who lacked what we would call hearing, or whose hearing operated in a different frequency range than ours, or who hadn’t any musical tradition at all. Even they could learn from the music by applying mathematics, which really does seem to be the universal language that music is sometimes said to be. They’d look for symmetries—repetitions, inversions, mirror images, and other self-similarities—within or between compositions. We sought to facilitate the process by proffering Bach, whose works are full of symmetry, and Beethoven, who championed Bach’s music and borrowed from it.

I’m often asked whether we quarrelled over the selections. We didn’t, really; it was all quite civil. With a world full of music to choose from, there was little reason to protest if one wonderful track was replaced by another wonderful track. I recall championing Blind Willie Johnson’s “Dark Was the Night,” which, if memory serves, everyone liked from the outset. Ann stumped for Chuck Berry’s “ Johnny B. Goode ,” a somewhat harder sell, in that Carl, at first listening, called it “awful.” But Carl soon came around on that one, going so far as to politely remind Lomax, who derided Berry’s music as “adolescent,” that Earth is home to many adolescents. Rumors to the contrary, we did not strive to include the Beatles’ “Here Comes the Sun,” only to be disappointed when we couldn’t clear the rights. It’s not the Beatles’ strongest work, and the witticism of the title, if charming in the short run, seemed unlikely to remain funny for a billion years.

“Dark Was the Night, Cold Was the Ground,” by Blind Willie Johnson

Ann’s sequence of natural sounds was organized chronologically, as an audio history of our planet, and compressed logarithmically so that the human story wouldn’t be limited to a little beep at the end. We mixed it on a thirty-two-track analog tape recorder the size of a steamer trunk, a process so involved that Jimmy jokingly accused me of being “one of those guys who has to use every piece of equipment in the studio.” With computerized boards still in the offing, the sequence’s dozens of tracks had to be mixed manually. Four of us huddled over the board like battlefield surgeons, struggling to keep our arms from getting tangled as we rode the faders by hand and got it done on the fly.

The sequence begins with an audio realization of the “music of the spheres,” in which the constantly changing orbital velocities of Mercury, Venus, Earth, Mars, and Jupiter are translated into sound, using equations derived by the astronomer Johannes Kepler in the sixteenth century. We then hear the volcanoes, earthquakes, thunderstorms, and bubbling mud of the early Earth. Wind, rain, and surf announce the advent of oceans, followed by living creatures—crickets, frogs, birds, chimpanzees, wolves—and the footsteps, heartbeats, and laughter of early humans. Sounds of fire, speech, tools, and the calls of wild dogs mark important steps in our species’ advancement, and Morse code announces the dawn of modern communications. (The message being transmitted is Ad astra per aspera , “To the stars through hard work.”) A brief sequence on modes of transportation runs from ships to jet airplanes to the launch of a Saturn V rocket. The final sounds begin with a kiss, then a mother and child, then an EEG recording of (Ann’s) brainwaves, and, finally, a pulsar—a rapidly spinning neutron star giving off radio noise—in a tip of the hat to the pulsar map etched into the records’ protective cases.

“The Sounds of Earth”

Ann had obtained beautiful recordings of whale songs, made with trailing hydrophones by the biologist Roger Payne, which didn’t fit into our rather anthropocentric sounds sequence. We also had a collection of loquacious greetings from United Nations representatives, edited down and cross-faded to make them more listenable. Rather than pass up the whales, I mixed them in with the diplomats. I’ll leave it to the extraterrestrials to decide which species they prefer.

“United Nations Greetings/Whale Songs”

Those of us who were involved in making the Golden Record assumed that it would soon be commercially released, but that didn’t happen. Carl repeatedly tried to get labels interested in the project, only to run afoul of what he termed, in a letter to me dated September 6, 1990, “internecine warfare in the record industry.” As a result, nobody heard the thing properly for nearly four decades. (Much of what was heard, on Internet snippets and in a short-lived commercial CD release made in 1992 without my participation, came from a set of analog tape dubs that I’d distributed to our team as keepsakes.) Then, in 2016, a former student of mine, David Pescovitz, and one of his colleagues, Tim Daly, approached me about putting together a reissue. They secured funding on Kickstarter , raising more than a million dollars in less than a month, and by that December we were back in the studio, ready to press play on the master tape for the first time since 1977.

Pescovitz and Daly took the trouble to contact artists who were represented on the record and send them what amounted to letters of authenticity—something we never had time to accomplish with the original project. (We disbanded soon after I delivered the metal master to Los Angeles, making ours a proud example of a federal project that evaporated once its mission was accomplished.) They also identified and corrected errors and omissions in the information that was provided to us by recordists and record companies. Track 3, for instance, which was listed by Lomax as “Senegal Percussion,” turns out instead to have been recorded in Benin and titled “Cengunmé”; and Track 24, the Navajo night chant, now carries the performers’ names. Forty years after launch, the Golden Record is finally being made available here on Earth. Were Carl alive today—he died in 1996 at the age of sixty-two—I think he’d be delighted.

This essay was adapted from the liner notes for the new edition of the Voyager Golden Record, recently released as a vinyl boxed set by Ozma Records .

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golden record

Where are they now.

• frequently asked questions
• Q&A with Ed Stone

What are the contents of the Golden Record?

The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University, et. al. Dr. Sagan and his associates assembled 115 images and a variety of natural sounds, such as those made by surf, wind and thunder, birds, whales, and other animals. To this they added musical selections from different cultures and eras, and spoken greetings from Earth-people in fifty-five languages, and printed messages from President Carter and U.N. Secretary General Waldheim.

"The spacecraft will be encountered and the record played only if there are advanced spacefaring civilizations in interstellar space."

Each record is encased in a protective aluminum jacket, together with a cartridge and a needle. Instructions, in symbolic language, explain the origin of the spacecraft and indicate how the record is to be played. The 115 images are encoded in analog form.

The remainder of the record is in audio, designed to be played at 16-2/3 revolutions per minute. It contains the spoken greetings , beginning with Akkadian, which was spoken in Sumer about six thousand years ago, and ending with Wu, a modern Chinese dialect. Following the section on the sounds of Earth , there is an eclectic 90-minute selection of music , including both Eastern and Western classics and a variety of ethnic music. Once the Voyager spacecraft leave the solar system (by 1990, both will be beyond the orbit of Pluto), they will find themselves in empty space. It will be forty thousand years before they make a close approach to any other planetary system. As Carl Sagan has noted, "The spacecraft will be encountered and the record played only if there are advanced spacefaring civilizations in interstellar space. But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet."

The definitive work about the Voyager record is "Murmurs of Earth" by Executive Director, Carl Sagan, Technical Director, Frank Drake, Creative Director, Ann Druyan, Producer, Timothy Ferris, Designer, Jon Lomberg, and Greetings Organizer, Linda Salzman. Basically, this book is the story behind the creation of the record, and includes a full list of everything on the record. "Murmurs of Earth", originally published in 1978, was reissued in 1992 by Warner News Media with a CD-ROM that replicates the Voyager record. Unfortunately, this book is now out of print, but it is worth the effort to try and find a used copy or browse through a library copy.

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Will Aliens Understand Voyager's Golden Record?

Could an alien observer truly understand the messages we have sent to the stars.

The Pioneer and Voyager spacecraft famously contain messages to anyone who might someday find them. Both Pioneers carry a plaque, while the Voyagers carry a phonograph record. An enormous amount of effort went into creating these objects, but could an alien observer truly understand the messages we have sent to the stars?

While we cannot take anything for granted when it comes to how these messages might or might not be interpreted, let’s assume that the beings who might find the spacecraft can at least see or hear with eyes or ears similar to our own. Each message was designed with not only the information it was to carry in mind, but also the means to establish understanding through common denominators found throughout the universe.

The Pioneer Plaque

Pioneer 10 and 11 each carry a 6 x 9-inch (15 x 23 centimeters), gold-anodized aluminum plaque. The plaque is affixed to support struts close to the spacecraft’s bus (main body). Carl Sagan and Frank Drake played key roles in designing the plaque and Linda Salzman Sagan, Sagan’s wife at the time, was the artist who actually drew the images engraved on the plaque.

The most striking feature of the plaque are the figures of the man and the woman overlying the silhouette of the Pioneer spacecraft itself. While this does clearly convey our physical size and shape, as well as that sexual dimorphism is present in humans, the facial features of the couple have little detail and the sort of sensory organs are being depicted (the couple’s ears are barely shown at all) might be unclear. The man and woman both have their mouths closed, and viewers might not understand that these are even mouths at all. Given how the image is drawn, an observer could also be forgiven for not understanding that both the male and female have hair on their heads.

The couple both have a bland expression (which may have been an attempt to avoid anything that could be interpreted as hostile) and the man is seen raising his right hand with the palm facing the viewer. While this gesture clearly conveys a greeting when viewed by another human, an extraterrestrial may have no way of interpreting this gesture. (Could you interpret a gesture made by an antelope … or a praying mantis?) It does show, however, that humans have opposable thumbs, as well as the general range of motion of the upper limbs.

With regards to the scientific data presented, the top left of the plaque shows the hyperfine transition of neutral hydrogen as a means of conveying to the reader baseline units of time (0.7 nanoseconds, the frequency of the transition) and distance (21 cm, the wavelength of the light released by the transition). If one is able to deduce that the image is that of hydrogen, the time and distance should be understandable.

The plaque also contains a map of our sun relative to 14 pulsars as well as the center of our galaxy, conveying both the distances to the pulsars and their frequency in binary notation. As this image conveys copious objective data, a spacefaring species might well be able to easily interpret it.

Finally, the plaque contains a map of the solar system. The solar system map is likely among the more easily interpreted parts of the plaque, with Pioneer shown to have originated from the third planet. The plaque was created at a time when Pluto was still considered the ninth planet (before the discovery of other trans-Neptunian dwarf planets such as Eris and Sedna, among others), but it would still direct the reader’s attention to Earth if they were able to figure out that our solar system was the one depicted.

Voyager’s Golden Record

The Voyager record asks more of whoever finds it but gives more information in return. These phonographs, attached to the spacecraft bus, feature a cover illustration and over 90 minutes of audio on the reverse side. The cover illustration features the same image of hydrogen and the same pulsar map as found on the Pioneer plaque. Of critical importance, the Voyager records convey instructions on how to play them, such as how to affix the attached stylus, at what rate of rotation the record must be spun, and the proper waveform of signals generated by the record. It also explicitly tells the reader how to know if they are viewing the images properly via an engraving of what the first image (a circle) should look like. While this may seem very daunting, the challenge is primarily technical and might well be easily overcome by an advanced spacefaring species.

An alien species might well find more difficulty in interpreting the audio samples, music, and images contained on the record. There are over 50 greeting messages in different languages. While the specifics of the messages are likely to be uninterpretable, they would at least convey to the listener the diversity of the creatures who created the Voyagers.

Similarly, the musical selections chosen demonstrate a wide range of human musical styles (ranging from works of Beethoven and Stravinsky to those of Chuck Berry, among others). While the lyrics of “Johnny B. Goode” are probably gibberish to an extraterrestrial, the beat and rhythm of the song would convey a tremendous amount to an alien listener.

Of perhaps the greatest importance are the 115 images encoded on the record. The first six images, if decoded properly, provide immense technical data for the reader regarding mathematical definitions, scales and sizes, as well as additional information regarding our location and how to find us. Images of the sun and its spectrum, as well as some of the planets in our solar system, could help the discoverer of the Voyagers to find us should they decide to pay the Earth a visit. There are also approximately 20 medical and scientific diagrams including the structure of DNA and detailed images of human anatomy. These images could likely be interpreted correctly given their concrete nature.

The Voyager record also contains a plethora of images of humans engaged in a variety of activities (including eating, looking through a microscope, and even going on a spacewalk). While many of these images would be hard to interpret (e.g., a picture of a woman licking an ice cream cone or a photo of a string quartet) the images would at least convey that humans have created a complex civilization with some degree of advanced technology.

The Big Picture

As Marshall McLuhan famously said, “The medium is the message.” While the recipients of the Pioneer plaque or the Voyager record might never understand everything we are trying to convey, the fact that these messages were placed on interstellar spacecraft carry (both for them and for us) a deeper message — that humans created these spacecraft and that we want to tell the universe who we are.

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Now You Too Can Own a Piece of Space History

The engraver who inscribed Carl Sagan’s and Frank Drake’s 1973 message to extraterrestrials is now taking orders

Jason Daley

Correspondent

In 1972 and 1973, Pioneer 10 and Pioneer 11 blasted into space with small gold-anodized aluminum plaques bolted to their antenna support struts. Designed by Carl Sagan and Frank Drake and illustrated by Linda Salzman Sagan, the plaques sported images detailing the location of Earth within the galaxy as well as images of a human woman and man. They were bolted to the spacecraft—the first to leave our solar system—in the off chance that an alien civilization found the probes.

But, as  Elizabeth Howell at Seeker reports, at the time only three of the plaques were created—two for the probes and one for NASA. Now, in honor of the Pioneer mission's 45th anniversary, a designer has teamed up with the plaque’s original engraver to create exact replicas.

According to the plaque’s page on Kickstarter , Duane King, who has done design work for companies including Apple and Nike, has been fascinated with space since he was a child—inspired by Sagan’s Cosmos series in the early 1980s. So King decided to make a replica of the infamous space plaque himself.

After finding a documentary about the image’s creation, he realized the man who made them might still be around. Turns out he was. King teamed up with engraver Ponciano Barbosa at Precision Engravers in San Carlos, California, to produce the images.

They are now taking orders for two versions of the plaque. The first is an exact replica of the six-by-nine-inch, gold-anodized aluminum plaque, which will be manually engraved by Barbosa and his team using the original 1972 design. Two-hundred of those are available for $399 each. Another batch will be produced by a laser-engraving machine and start at $99. The Kickstarter is now well over its $70,000 production goal.

According to  The Planetary Society , founded by Sagan, the idea for the plaque was suggested to him just a few months before the launch of Pioneer 10. Sagan brought the idea to NASA, which thought it was cool. So Sagan, along with Cornell University professor Frank Drake and Sagan’s wife Linda, who is an artist and writer, assembled humanity's message to the universe in just a few short weeks. 

In the upper left of the plaque is an image of hydrogen atoms in two energy states—a universal constant for space and time. When hydrogen atoms change states, electromagnetic radiation is released. And this wave of radiation is the basis for measurement for the rest of the plaque: The radiation lasts 0.7 nanoseconds (basis for time) and extends roughly 21 centimeters (basis for length). 

The plaque shows a woman standing eight of these hydrogen units tall, or five feet five inches tall. It also shows the height of the naked, ethnically ambiguous humans in relation to the Pioneer probe itself.

There is also a star burst of lines and dashes, which indicates the distance of our Sun to pulsars—neutron stars that emit regular burst of radiation—within our galaxy as well as a diagram of our Solar System showing that the probe comes from the third planet from the Sun.

The Planetary Society writes that it’s highly unlikely that anyone will ever find the craft and it will probably be lost in the “immense tranquility of space." But the plaque does have significance. “The message we sent to the universe still echoes in our ears. Born from such a mission—one that spans space, time, and perhaps, civilizations—is a new mindset, an otherworldly perspective,” they write.

As Howell reports, NASA lost contact with Pioneer 11 in 1995 and Pioneer 10 winked out in 2003. When the Voyager 1 and Voyager 2 spacecraft launched in 1977, they carried with them an even more sophisticated attempt to communicate with extraterrestrials, also created by Sagan. Those missions sent up gold records containing the sites and sounds of Earth. Last year, more than 10,700 people donated to Kickstarter to receive a 40th anniversary replica of that record. The project raised more than $1.3 million.

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Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover , Popular Science , Outside , Men’s Journal , and other magazines.

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Original research article, introducing humans to the extraterrestrials: the pioneering missions of the pioneer and voyager probes.

• 1 Department of Anthropology, Durham University, Durham, United Kingdom
• 2 The Pufendorf Institute for Advanced Studies, Lund University, Lund, Sweden

This article gives a brief overview of how human life is represented on the 1972 Pioneer 10 and 1973 Pioneer 11 plaques and on the 1977 Voyager 1 and 2 Golden Records, sent on their journeys to deep space by the U.S. National Aeronautics Space Administration (NASA). Having left the boundaries of the Solar System and moving through interstellar space, the space probes still carry messages with information about their makers and their era. After a description of the two famous American interstellar messages, this article gives a basic introduction to their contents using some of the photographs available in the public domain. The overview includes the visual and audio part of the Voyager message and is focused around the questions for what types of information were included, what methods were used to communicate the information and how were humans introduced to the unknown receiver.

The Pioneering Missions of the Pioneer and Voyager Probes

Human fascination with, and curiosity about, the yet unanswered question about whether we are the only life forms and the only intelligent species in the Universe has been puzzling generations of thinkers, scientists, and writers. Are we alone? Is there other life out there? If yes, what is it like? Is it humanoid? With the advent of the Space Age, era beginning in the form of the first space travel in 1957 (Sputnik 1) and the concurrent advancements in space technologies, it became more plausible for scientists to take on the age-old question and attempt to actively search for life beyond our planet. Among the first methods that were used was to send a message using either vehicles used for travelling in space or to transmit a signal via radio telescope.

In 1972, the National Aeronautics and Space Administration (NASA) launched the Pioneer 10 spacecraft on its mission to Jupiter, as NASA’s first mission to the outer planets. Its twin, Pioneer 11, followed 1 year later. After successful exploration of the Jovian system, the Pioneers continued their journey to Saturn, Uranus and beyond, into deep space. The Voyagers were launched in 1977 with the primary mission objective to “extend the NASA exploration of the Solar System beyond the neighbourhood of the outer planets to the outer limits of the Sun’s sphere of influence, and possibly beyond.” 1 Until 1998, when the Voyager two that travels at higher speed got ahead, Pioneer 10 held the primacy in being the most distant spacecraft from earth. Heading for the Aldebaran, in Taurus (The Bull) constellation, NASA estimates it will take Pioneer 10 over 2 million years to reach it 2

The Pioneer and Voyager missions hold important positions in space exploration and together with science data delivered, they made many historic firsts such as the first Jupiter flyby (1973, Pioneer 10), the first Saturn flyby (1979, Pioneer 11), the first photograph of the whole Solar System (1990, Voyager 1), the famous Pale Blue Dot photo on which the earth appears as a bright pixel (1990, Voyager 1). In 2012, Voyager 1 became the first manmade object to have entered interstellar space.

Another thing makes those two space missions special: the messages mounted on the exterior of both Pioneers and Voyagers ( Figure 2 and Figure 3 ). Alike in form, yet different in the volume of information provided, the task of these metal artefacts is to inform the receiver about the creators of the spacecraft. Beyond any doubt, the scientific team in charge of message development led by Carl Sagan embarked on a challenging endeavour. Together with the technological challenges, many questions arise. Firstly, how to represent our lifeforms to other imagined lifeforms, separated from us by time, space and biological and cultural factors beyond our imagination. What methods, channels to use? Secondly, an equally important question, namely to describe what human life is like. Who are we? What do we have in common? What is life on Earth like?

The Interstellar Artefacts

Now mostly referred to as the Pioneer Plaque, a small gold-anodised aluminium plate was mounted on each spacecraft. The inscriptions feature the nude figures of a human male and female along with several symbols that were designed to provide information about the origin of the spacecraft. Described by NASA as “a mark of Man,” the plaque was authored by a small team consisting of astronomer and science populariser Carl Sagan and American astronomer and astrophysicist Frank Drake ( NASA 1977 ). Drake, also known as the author of an equation which estimates the number of advanced civilisations in the Universe formulated in 1961 3 and 4 pioneered the use of radio telescopes in the Search for Extraterrestrial Intelligence (SETI) that started in the 1960s. Artist Linda Salzman Sagan, wife of Carl Sagan, created the artwork for the plaque.

Sagan, pictured below holding the Pioneer Plaque ( Figure 1 ), later became chair of a committee that compiled a message that travelled to outer space aboard Voyager spacecrafts. Drake also remained involved in the Voyager committee. According to NASA’s mission report, the history of the making of the Pioneer message was of short duration ( NASA 1977 ):

FIGURE 1 . Carl Sagan holding the Pioneer plate. Credit: NASA.

“Dr. Sagan also was enthusiastic about the idea of a message on Pioneer. He and Dr. Drake designed a plaque, and Linda Salzman Sagan prepared artwork which was presented to NASA which accepted it for this first spacecraft from the Solar System into the Galaxy.”

The plate, only fifteen by 23 cm big, presents five engraved diagrams as can be seen explained in Figure 2 , informing about the existence of humankind and its location in our Galaxy. In the upper left corner of the plate, we see two connected circles that show a hyperfine transition of neutral hydrogen (used as a standard unit for measurements of time and distance). The radial diagram below is actually a map that gives the position of our Sun shown in relation to fourteen pulsars. Pulsars are fast rotating degenerated stars that emit regular pulses and hence are used as stellar beacons.

FIGURE 2 . Line drawing of the Pioneer plaque with explanatory callouts. Credit: NASA History.

In the bottom part the planets of the Solar System are displayed, starting with the Sun on the very left. The line with the arrow points to the origin of the spacecraft from the third planet. The Pioneer spacecraft silhouette shown in the upper right part accompanies a couple of Earthlings with the male representative friendly greeting the inhabitants of other worlds. Located on the right is a small diagram that represents the binary equivalent of decimal eight. The “hydrogen wavelength multiplied by the binary number representing eight alongside the woman, gives her height,” as explained in the NASA Pioneer mission report ( NASA 1977 ). The same technical report also describes that the Pioneer plaque: “represents at least one intellectual cave painting, a mark of Man, that might survive not only all the caves on Earth, but also the Solar System itself. It is an interstellar stela that shows mankind possesses a spiritual insight beyond the material problems of the age of human emergence.ˮ

Sagan himself said that the chances of a Pioneer spacecraft being detected are remote, but if it were to happen, would the recipients know what the engravings on the plaques represent or were meant to represent? Will they be able to make sense of a radial diagram, mysterious symbolism and a silhouette, and do we, natives of a culture that produced such a message, understand the meaning of Pioneer diagrams when presented to us without any prior knowledge of its intended meaning or further explanation? At first sight, the engraved plate may seem rather elementary, especially when served with the explanatory callouts. Yet there is a number of qualities and conditions that the receiver would have to possess to be able to find, read and understand such a message ( Capova 2013 ).

Firstly, and it might be regarded as axiomatic, advanced technology and equipment is required to detect and intercept the Pioneer spacecraft. Secondly, eyes, or an organ of sight, is needed to recognise or see the engravings. Thirdly, and it may sound as an absurd statement, the receiver will have to be interested in reading such messages, be curious about what those engravings mean and be willing to attempt to unravel the meaning of symbols. Especially the science concepts, such as the hyperfine transition of neutral hydrogen, map of nearby pulsars and Solar System map, require having background in science, abstract thinking, intellectual curiosity, and creativity. These prerequisites reveal that science as “collective empiricism” that involves “investigators dispersed over continents and generations” ( Daston and Galison 2007 ) is considered as an universal language; and hence it could be also the only language we would have in common with the (assumed) recipients of the message.

The Voyager’s Message in a Bottle

In 1977, the Voyager messages set off on their mission to explore the gas giants Jupiter and Saturn and later to continue towards the outermost edge of the Solar System. The record contents were created and assembled for NASA by a committee chaired by Sagan and the scientific team: Frank Drake, Ann Druyan, Timothy Ferris, Jon Lomberg, Linda Salzman Sagan. Drake is the author of some diagrams from the visual part, specifically of mathematical definitions. Lomberg, US space artist and designer, created the record’s diagrams. International consultations have taken place to accomplish the objective.

While the Pioneer information plaque is composed of engraved symbols, the idea for Voyager was to include a comprehensive description of life on earth, not solely focused on humans but also giving the wider context. A combination of media, visual and audio, were included to portray the complexity and diversity of life on earth and to describe humans and their planet. The messages are in fact time capsules, intended for “future times and beings” as Carl Sagan said about the Voyagers (1978), in a sense immortal sentiment that we have left behind.

Playing the Golden Record

The Voyager message consists of a phonograph record with complex audio-visual information. The key to unlocking the message rests engraved on the protective aluminium jacket of the message, the interstellar envelope ( Figure 3 ) where we can recognise the pulsar map and time reference diagram used for the Pioneer plaque. Six of the eight diagrams give instructions for how to assemble the phonograph and play the record ( Figure 4 ). There is an outline of a cartridge with stylus using both side and front elevations. Once the phonograph has been assembled, using the record, a cartridge and a needle provided in the case, the next step for the receiver is to see the contents electronically placed on the record.

FIGURE 3 . The protective cover with instructions, mounted on Voyager spacecraft. Credit: NASA JPL.

FIGURE 4 . Explanation of the voyager golden record cover diagram. Credit: NASA JPL.

The gold-plated copper disk hidden under the cover, known as the Golden Record ( Figure 5 ), has its contents divided into four sections:

• Scenes from Earth—118 images and diagrams about our species and our planet (including basic mathematical, chemical, and physical definitions).

• Greetings from Earth—spoken greetings from Earth-people in fifty-five languages and printed messages from US President Jimmy Carter and UN Secretary General Kurt Waldheim.

• Music from Earth—musical selections from different cultures and eras (27 audio recordings of Eastern and Western classics and a variety of ethnic music).

• Sounds of Earth—a variety of natural sounds (21 audio recordings of human activities, machines, and natural phenomena).

FIGURE 5 . The golden record. Credit: NASA.

The Scenes from Earth comprise one hundred and eighteen pictures in total out of which seventeen are descriptive, black and white, two-dimensional diagrams created by the scientific team. The remaining pictures are colour photographs from various sources. If properly decoded and played, the first picture of the message, the “Calibration circle” appears. A simple, black and white line drawing of a circle, reproducing the shape of the record itself, is the encouraging sign that the message was decoded properly and the Scenes from Earth open. The introductory slide is followed by definitions of basic mathematical concepts, physical units and quantities, and two diagrams of “Solar system parameters” that show the Sun and (then) nine planets. The diagram is then followed by individual photographs of Solar System objects; Sun, Mercury, Mars ( Figure 6 ), Earth ( Figure 7 ), and Jupiter.

FIGURE 6 . Mars. Credit: NASA.

FIGURE 7 . Earth. Credit: NASA.

When examining the photographs, the viewers can see that explanatory symbols, e.g., mathematical definitions or chemical formulas, were inserted directly into the picture. For example, the photograph entitled “Egypt, Red Sea, Sinai Peninsula, and the Nile” on Figure 8 provides a description of the chemical composition of Earth’s atmosphere. The top left tag shows that nitrogen (N 2 ) accounts for 78% of the atmosphere (N 2 78/100).

FIGURE 8 . Egypt, red sea, sinai peninsula, and the nile. Credit: NASA.

Subsequent to the astronomy basics are the definition of chemical units created by Drake. The models of chemical elements include: hydrogen (H, the simplest and most abundant element in the Universe), carbon (C, occurs in all organic compounds), nitrogen (N, a constituent of all living tissues), oxygen (O, the most abundant element in the earth’s crust). A model of phosphorus (P), an element that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells, was also incorporated into the diagram. Why use chemistry? The chemical elements here demonstrate the basis of life because they in combinations constitute all matter. These elements are known as the fundamental building blocks of life. There is another crucial motive emerging from this pictorial sequence, and that is the description of humans as “carbon-based” life forms.

The two pictures of the DNA Structure (deoxyribonucleic acid) were created by Lomberg. The DNA molecule is associated with the transmission of genetic information and carries genetic instructions in all living things. Next picture shows the microscopic detail of cells and their division. It is followed by twenty images that describe human life on planet earth. Nine of the pictures document human anatomy, and are followed by reproduction and procreation: in other words, the story of life. 5

Life Creation: the Voyager Story

The set of pictures dedicated to “life creation” shows cell division, human anatomy, and human sex organs. Human anatomy is illustrated using encyclopedic entries from the World Book encyclopedia ( Sagan and Drake, 1975 ). The diagram of conception explains the size of sperm and shows how it penetrates the egg. The picture of “Fertilised ovum” shows the fertilised egg at two stages: one second, immediately after conception, and time until the first of cell division, indicated with the tags “1 s” and “43200 s.” The portrayals of conception and fertilisation are models that can be found in biology school books.

The viewers notice here that the visuals are presented in two forms. The first one is true, colour photographs that record the moment or events. The second one consists of schematic representations, black silhouettes on a white background based on the photographs (e.g., the Fetus and Silhouette, the Diagram of family ages). The explanatory labels and descriptions were inserted directly into the photographs such as height, mass (mathematical notations). All pictures are marked with numbers that show their order.

The representation of the foetus is also both symbolic and authentic; the diagram includes description of the foetus and its evolution in time and its growth, using numerical legends to indicate its development up to 5 cm in size. We can understand those images on two levels. Firstly, it describes that humans reproduce and secondly that humans comprehend and conceptualise the process of reproduction. By doing so, these pictures illustrate how science is done, communicated and visualised; science as a shared “collective empiricism” ( Daston and Galison 2007 ).

The visual narrative of creation of human life consists of nine pictures. The preceding descriptive anatomical part includes eight pictures and presentes details of the bodily structure of humans. The “Diagram of male and female” is a black and white silhouette of a heterosexual couple holding hands surrounded by symbols indicating the sex, age, and height of the two figures. The female figure has a foetus in her womb. The purpose of the diagram is to underline the biological fact that people have children. The tags also tell us that male is 160 cm tall and 20 years old, while the female is 155 cm tall and of the same age. The image entitled “Birth” shows a surgeon wearing a surgical mask, assisting with the delivery. Here we can observe that giving birth to a child at a hospital displayed here was considered the most common option in developed countries. The emphasis given on medical assistance during birth of a child is a traditional medical practice typical in the Western societies.

The further bond and care of mother for the child and the role of the father are documented in two pictures: Nursing Mother and Father and daughter (from Malaysia), both presenting another fact: parents care for their offspring. It is worth mentioning that there is a link between the picture of “Nursing mother” and one of the audio tracks. The recording features a crying baby and a mother’s voice talking to the child yet the spoken language is English.

Succeeded to the life section are pictures that refer to family or community, It consists of five items–“Nursing mother,” “Father and child,” “Group of Children,” “Diagram of family ages,” and “Family portrait.” On the representation of the family, we can observe directly the link between the last two presented pictures. The “Diagram of family ages” shows four silhouettes of persons that were transposed from the “Family portrait” photograph. This explanatory diagram, created by Lomberg, specifies the age and weight of four family members using the numerical legends. Written in English (y for years and kg for kilograms), the tags introduce two children aged 4 (225 kg) and 12 years (385 kg), and two women aged 30 (545 kg) and 80 years (425 kg), indicating generation of ancestry: a mother and grandmother.

The Story Continues: Nature, Society, and Technology

Right after the family photo follows the “Continental Drift” diagram that presents the position of continents in the distant past, present and remote future. This is a visual quote of the original informative plaque arranged by Sagan for the LAGEOS I Satellite (Laser Geodynamic Satellite) put in Earth’s orbit in 1976, intended as a legacy for future generations of humans. The diagram opens the documentary presentation of the natural world and the environment: “Heron island,” Seashore,” “Snake river and Grand Tetons,” “Monument Valley,” “Forreste scene with mushrooms,” “Fallen leaves,” “Tree with daffodile.” Also, the human place and activities in nature were portrayed here. The lighthouse on a seashore, the equestrian moving through sand dunes, the shepherds in Monument Valley, and the gardener raking the fallen leaves.

Picture of “Flying insect with flowers” opens the animal life section along with the diagram of the “Vertebrate evolution.” This diagram, outlining the evolutionary sequence is interesting for one more reason: the male-female figures were placed at the top right of the image. Here we meet again the same pair that was displayed on the Pioneer plaques but in this Voyager diagram, it is the female representative of humankind who salutes the recipient. Coloured photos of “Dolphins,” “School of fishes,” “Tree toad,” “Crocodile,” and “Eagle” represent the biological diversity on Earth. The interactions and contact between humans, fauna and flora are again shown on several pictures such as “School of fish” (with diver), and “Jane Goodall and chimps.”

Photo of “Bushmen hunters” - again with a silhouette - unlocks the picture gallery of peoples from all around the world. The viewer of this spectacular slideshow can see faces of people from Guatemala, Bali, Thailand, and Turkey and their daily activities. Not only hunting, walking, working, dancing, climbing, and exercising (performance by “Gymnast”), running (“Sprinters”) is portrayed in these pictures, and then teaching, learning, fishing, cooking, shopping at the supermarket, eating dinner in China. Besides activities, pictures show contacts among people, their communities (dinner, schoolroom, “Children with globe”) or their interactions with the environment and animals (harvest, fishing) and with the natural world in general, such as a photograph of a diver and sea fish and a man walking in the forest.

The section dedicated to people of Earth in their natural environment fluently moves to the description of buildings and structures. Here we can observe the shift from “nature” (natural) to “technology” (artificial). The photo of the “Great Wall of China” is followed by house constructions in Africa and Amish Country, and by images of a finished house (American) and its interior. Not only buildings like the Taj Mahal and the UN centre both in daylight and at night, but also cities were incorporated into the photo gallery: Oxford and Boston. The photo of the Opera House in Sydney, the demonstration of modern architecture opens the technical part.

The story about engineering and technology starts with photos of an artisan with a drill, factory interior filled with machines, a museum exhibit, X-ray of a hand, and a woman with a microscope. An important part of the compilation is the means of transport and transportation networks - traffic jam from India, highway, jet fighter, train, Titan spacecraft (the booster rocket of both Voyagers, Figure 9 ), airport, and bridge. Communication engineering was not left out as we can see from the photo of the Arecibo Telescope used to transmit the first radio message to extraterrestrials together with photos of the Westerbork radio telescopes from the Netherlands.

FIGURE 9 . Titan Centaur launch. Credit: NASA.

Closing moments of the visual presentation are dedicated to photos of “Page of book” from the System of the World by Isaac Newton, an astronaut floating in space ( Figure 10 ), “Sunset with birds,” and “String Quartet.” The final picture of the Golden Record’s visual part is the “Violin with the music score.” The photo of the musical sheet of Cavatina composed by Ludwig van Beethoven closes the visual part and opens the acoustic anthology.

FIGURE 10 . Astronaut in space. Credit: NASA.

The Interstellar Best of: Sounds, Greetings, and Music of Earth

The first audio part includes twenty-one sound recordings: “Sounds of earth.” The total playing time is nearly 13 min of various sounds. Similarly, to the picture sequence the sounds’ compilation follows the chronological order and seems to favour the historical perspective. According to Sagan, some of these sounds had been present on earth since prehistoric times. The noises of volcanoes, earthquakes, thunders, mud pots and atmospheric wind, rain and surf correspond to natural phenomena. Furthermore, the record includes sounds uttered by animals: frogs, elephants, and chimpanzees, howling of hyena, barking of domestic dogs, and singing of birds. Some of the named animals were portrayed in the visual part.

The evolutionary symphony opens with beats of the first stone tools (sound of flint cracking) and continues with sounds of a blacksmith, sawing, and sheep herding ( Sagan et al., 1978 ). The human activity of the advanced ages is represented by sounds produced by tractor, riveter, ship, train, bus, car, F-111 Flyby, and Saturn five Lift-Off. Sounds of footsteps, heartbeat, laughter, fire, speech, sound of kiss, mother talking to a child (as mentioned earlier), are documents about human life on planet earth. The last soundtrack contains the recording of electrical activity of the human brain that was transferred to sound, intended as a life sign.

The “Greetings from earth” contains spoken reports by representatives from our planet, the section includes fifty-five greetings in most spoken languages and one in a whale language. The total time of recorded greetings is about 4 min. The shortest recording only consists of a simple “Hi!ˮ with 15 s of length. The longest greeting is in Gujarati, one of the most spoken languages in India. There was no uniform choice behind the greetings composition and the speakers were given no specific instructions as to what to say ( Sagan et al., 1978 ). The speakers were chosen on the basis of their fluency in the language. Each greeting has its inherent characteristics, possibly expressing also the common greeting formulas of the given language. Some of the greetings are recipient oriented. For example:

English: “Hello from the children of planet earth.ˮ

Swedish: “Greetings from a computer programmer in the little university town of Ithaca on the planet earth.”

Czech: “Dear Friends, we wish you the best.ˮ

Amoy (Min dialect): “Friends of space, how are you all? Have you eaten yet? Come visit us if you have time.ˮ

Latin: “Greetings to you, whoever you are; we have good will towards you and bring peace across space.”

Like the visual slide show, the third audio compilation, “Music from earth,” was intended to offer the auditorium a fine terrestrial selection. Twenty-seven tracks add up to nearly 90 min of music. The musical performances include Western classical “the best of” collection, popular rock-and-roll songs, and native music typical in various geographical areas. The classical music compilation meets the high standards requirements not only on quality and popularity of music: Queen of the Night aria by W. A. Mozart, Fifth Symphony by L. van Beethoven, Brandenburg Concerto by J. S. Bach but on the reputation of interpreters and conductors (Gould, Moser, Richter, Stravinsky). The Western composers treated with partiality were Johann Sebastian Bach (three tracks) and Ludwig van Beethoven (two tracks).

The selection of music not rooted in traditions of Western culture offers a diverse and melodic set; the audience were offered Aborigine songs, Azerbaijan bagpipes, Georgian chorus, percussion from Senegal, Pygmy girls’ initiation song from Zaire, Night Chant by Navajo Indians, music from Java Mexico, New Guinea, Japan, Bulgaria, China, and India with contents of the lyrics untranslated. To Beethoven is dedicated not only to the last picture of Scenes from earth but also the last track from Music from earth: Cavatine, a short and simple song that is said to be the only one piece that made its composer cry.

Adam and Eve of the Space Age

The controversial engraving of a naked earthling pair provoked much discussion and caused public indignation ( Havel 1996 ). The ambivalent reactions of the public on the Pioneer plaque together with the copyright restriction appear to be the reasons why the public were not informed about the final contents of the Golden Record until the moment the Voyagers were safely put beyond earth’s orbit. Despite the initial public reaction, this image has become a symbol of the active search for life beyond earth and to this day continues to be one of the visual icons of the Space era.

The significance of the “couple of Earthlings” is also illustrated by the reuse of the very same representation in other messages, such as the Cosmic Call radio message. While Pioneer and Voyager are the material objects, manufactured messages attached to a spacecraft as a plaque, plate, or record; the second method of sending messages to outer space is radio broadcast. A “radio message” is a signal transmitted by a radio telescope. The transmissions are often referred to as a more efficient method of search for extraterrestrial intelligence because the signal travels at the speed of light, the maximum known velocity. The historically first radio signal aimed at another civilisation left earth in 1974 from the large radio telescope in Arecibo, Puerto Rico, a part of the National Astronomy and ionosphere Centre (NAIC), designed by Drake.

The visual quote of Pioneer’s greeting couple ( Figure 11 ) can be found in the opening of the Cosmic Call radio message written by Canadian astrophysicists Yvan Dutil and Stephane Dumas and first broadcast in 1999. The Cosmic Call message was intended to be an update of the Arecibo message and therefore is larger in size, duration, and scope. The original twenty three pages long Cosmic Call one was updated 4 years later. The message contained photos, drawings, audio and video files that were submitted by the Team Encounter members worldwide, and in 2003 rebroadcast again. The images below present the Adam and Eve of the Space Age as portrayed on the original Pioneer Plaque (1972) and Cosmic Call in 1999 (and 2003) ( Figure 12 ).

FIGURE 11 . The detail of Pioneer Plaque, the greeting couple of Earthlings. Credit: NASA.

FIGURE 12 . The greeting couple, Cosmic Call (1999). Credit and Copyright: Y. Dutil, S. Dumas.

The figures of human procreation are well debated in academic literature, popular media, and academic publications. While they were intended to present representatives of Earthlings, they can be seen as a clear manifestation of 1970 s Western normativity as far as gender, ethnicity, and sexuality are concerned. The human bodies as well as the sexes are portrayed within conventional and stereotyped understanding the sexual dimorphism and fixed into idealised form without any abnormalities. Presented also on the Voyager Message in 1977, this variation of the procreation couple, described by Michael Warner in the introduction to the “Fear of Queer Planet” as a clear manifestation of “heteronormavity” ( Warner and Collective 1993 : xxiii). The story of life is presented in a rather utilitarian fashion with biology, uniformity and function being preferred over culture, variety and context. For example the cultural context of reproduction that is the institution of marriage, was missed out too.

The enduring American cultural icons, the messages continue in their pioneering voyage through interstellar space and terrestrial media and art alike. They did not escape the attention of science fiction writers, notably the closing scene of the 1979 full-length Star Trek: The Motion Picture ( Star Trek, 1977 ). At the end, a superior extraterrestrial being returns the Voyager probe (V-GER) to its home planet with its message unread.

The messages can be also viewed from another perspective and that is their biblical allusion and mythological significance. In the case of the Pioneer and Voyager (and Cosmic Call) messages, the duality of sexes was pointed out, and the Voyager message presents a narrative about what makes humans human, the life events and activities inherent to humanity. Berger in his study of narratives in popular culture analysed the symbolism and mythical aspect of the Apple Inc. 1984 commercial and in particular the Apple logo, a study that gives an interesting parallel to how to interpret the interstellar story ( Berger, 1997 ). Berger argued that the logo “also has an intertextual and in this case mythological significance, because it also alludes to Adam and Eve in the Garden of Eden” (1997:119). The Pioneer Plague and Voyager Record, both carry an image that when approached in terms of its intertextual connections can be interpreted as a creation story. In this context the mythological aspect of the image of the couple, the biblical allusion of Adam and Eve, here in the center of a Space age narrative ( Capova, 2013 ).

Even today the legacy of Voyagers lives on. To celebrate the 40th anniversary of Voyager 1’s launch, NASA launched a space social media campaign using Twitter, Instagram, Facebook, Google + or Tumblr. The public were asked to submit a brief and uplifting text tagged as #MessageToVoyager. The winning messages selected by popular vote were beamed towards Voyager one into interstellar space on August 5, 2017. The Star Trek star William Shatner, known as Captain Kirk of the Starship Enterprise assisted with the broadcast.

The Commonalities

The symbols of neutral hydrogen as a universally recognisable constituent of the Universe, the map locating earth using near and recognisable stellar objects, the procreation couple greeting the extraterrestrials–it all presents a story. We have seen that the images were used to convey information, to explain and to interpret. Sounds, spoken word and music as an alternative to diagrams and photos seems to have a specific role in the message design. Similar to written language, musical notation or a music sheet can be reproduced by anyone who knows how to read and interpret the symbols.

Science was set as the preferred universal language and for decades to come also became a blueprint of interstellar communication. A good example is the model of neutral hydrogen. The time-period measurement is explained using the period associated with the fundamental transition of the hydrogen atom that provides the basic time reference. The hydrogen symbol is accompanied by the location of earth, both adopted from the Pioneer plaque. The map is created by using the neighbouring rotating stars that emit electromagnetic radiation known as pulsars, to locate our planet within the galaxy. The images below illustrate that the hydrogen clock and pulsar map symbols were presented on the Voyager protective cover ( Figure 13 ) and Pioneer plaque ( Figure 14 ).

FIGURE 13 . The Pulsar Map and Hydrogen Symbol. Segment of the Voyager message inscription (1977). Credit: NASA.

FIGURE 14 . The Pulsar Map and Hydrogen Symbol (1972 and 1973). Segment of the Pioneer plaque engraving. Credit: NASA.

Numbers were proposed as a language suitable for interplanetary and later interstellar communication, or as Samuels described it: “a lingua franca for this communication” ( Samuels 2005 ). We can also evaluate the concept of the other lifeforms or receivers of the messages - advanced, scientific, extraterrestrial civilisation ( Capova 2008 ) that possesses the same “shared codes” ( Samuels 2005 ).

The time reference points to another important characteristic of the story of humanity and that is the ascending tendency within linear understanding of time. The perception of time among different cultures has been studied by anthropologists who highlighted the differences in understanding the time. Namely, the cyclical conception of time as a perpetual repetition corresponding to seasonal rhythms. The role of the ritual circle on Hawaii Islands was described by American cultural anthropologist Marshall ( Sahlins, 1981 ). Or Balinese concept of time and calendared system studied by Clifford ( Geertz, 1973 ), who discovered the varieties in actual day length that imply the different concept of duration and flexible units of time. Also, the Scenes from earth proceed as a series of events that are leading towards something: from the basics to the diversity, from the wild nature to technological development; the idea of progress.

The social studies of science and technology and philosophy of science have described the role of sciences as fundamental pillars of recent Western development and out of which also emerge the key values: rationality, empiricism, secularity, and the idea of continuous progress ( Schech and Haggis 2000 ). The light of reason as a basis of scientific deliberation is a core scientific value and a principal inheritance of the Enlightenment, a European intellectual movement of the late 17th and 18th centuries emphasizing reason and individualism rather than established doctrines.

The Voyager’s story of life was told along the developmental line with its main plot being advancements, technological development, science, knowledge of concepts of laws of the Universe, all described by languages of contemporary science. Of course, the message design is based on two unavoidable assumptions. First is the biological constitution of the receiver who possesses the capability to perceive and investigate, or is curious about what the messenger floating in space has to say about its senders. Second is the intelligence, or intellectual constitution that is shaped by a contemporary Western type of science education. In other words, the extraterrestrial lifeform has to have a sense of sight that facilitates the visible or “seeing,” and the sense of hearing that facilitates audibility or “hearing” and “listening.” The receiver is a priori burdened with the human qualities of the physical body, with a brain producing an intellect; and sophisticated and organised knowledge of the physical and natural world, that is science. The extraterrestrial being is required to see, hear, think, read, interpret, and understand ( Capova, 2013 ).

Interstellar Museum Exhibit

Let us suppose that the content of the Voyager message can be viewed like a museum exhibit. We have just finished a walk through this museum that exhibits colourful photos and cultural artefacts from the American era of the 1970 s. The collection on display, accompanied by fine musical selection played in the background, originates from various, yet not recognised places and peoples. As the visitors walk through the museum, they read the “legends” attached to each of the pictures that give information about the exhibit, about its place of origin, their dating, history, and supposed use. At the end of the exhibition, the visitor may be fascinated by the wonderful diversity of nature and cultures and feel enthusiastic and overwhelmed by the extent of the exhibition. Some visitors may think that the museum contains sufficient information about our world, but others may consider the following.

First, the compilation itself is not extensive enough, inevitably there were many “photo exhibits” left in the museum depository simply because there is not enough space to display them all. Despite attempts to describe “life” there is one thing that was missed out entirely. The Golden Record does not contain any relevant information about dying and death. There are indications of this basic fact of all life (e.g., hunting, eating), yet without mentioning the fundamental fact of life, the message paradoxically cannot claim itself to be a complete story of human life. The message does not refer to any negative characteristics of humankind such as conflicts, hostility or war. The idealised part of humankind was demonstrated intentionally in order to present “a hopeful rather than a despairing view of humanity and its possible future” as Sagan explained (1978). For this reason, no references to war or conflict were mentioned either. The Voyager message shows only positive values, knowledge and progressive development of contemporary Western or scientific society.

Secondly, references to religious or spiritual life and/or ritual behaviour have been entirely excluded from the human story other than indirect symbolics and possibly also the role of music. Given the undebatable presence of religious and spiritual beliefs in human societies, it is a question why such a crucial aspect of human life has been omitted entirely? One explanation could be that the dominating view - the one of science - was the deciding factor to omit religion and religious considerations, in favour of scientific rationality and secularity.

The third point is quite simple. The contents selection was unavoidably biased by the Voyager committee, by their expertise, professions, and even by their beliefs about the nature of our lived world. For this reason, the life story offers more than just a mere description of “life” but also the interpretation of what “life” consists of. Not only the photographs and diagrams but also the use of several definitions (mathematics and chemical formulas as conventional designations) underline the rational understanding, scientific description of the world as the basis of the content selection inscribed scientific knowledge ( Macauley, 2006 ). Science is regarded as the universal language, even in the case of interstellar information relay.

The messages are period pieces. As a product of their era, they have faithfully captured the thinking, knowledge and even scientific paradigms of their era. One example of such a paradigm and its shift in case of astronomy can be seen in Drake’s representation of the Sun with nine planets. In 2006, the International Astronomical Union, drafted a new definition of a planet and consequently decided by vote that Pluto does not meet the requirements for a planet. That means that the scientific paradigm has changed and the Solar System currently consists of eight planets. As a consequence, the model of our star system placed on Voyager probes is no longer considered a valid paradigm.

Rather than offering mere criticism of choices made by the Voyager committee, or proposals of what should have been sent, this brief analysis concludes with an invitation to understand the Voyager message as a linear narrative of human curiosity presented by a small group of people who took on the challenge to present our world to unknown receivers.

Loyal to their disciplinary boundaries, the committee members have, rather than the variety of lives and cultures on earth, presented a success story of contemporary Western societies and its sciences. As Sagan rightly noted, different people in different points in history would have made different choices. And their choice was to send this description of what life meant to them at that time – a colourful scientific mosaic of life on earth frozen in time.

Data Availability Statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

Author Contributions

KAC has written this based on her MA and PHD research.

Conflict of Interest

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Abbreviations

JPL, Jet Propulsion Laboratory; METI, Messaging Extraterrestrial Intelligence; NAIC, National Astronomy and ionosphere Centre; NASA, National Aeronautics Space Administration; SETI, Search for Extraterrestrial Intelligence.

1 Source and more information on Voyager 1 and 2 missions is available from NASA Voyager Mission website: https://www.nasa.gov/mission_pages/voyager/overview

2 Source and more information on Pioneer 10 and 11 missions is available from NASA AMES Missions Archive: https://www.nasa.gov/centers/ames/missions/archive/pioneer.html

3 The Drake equation is a probabilistic argument used to arrive at an estimate of the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. The Drake Equation estimates N, the number of transmitting societies in the Milky Way galaxy.

4 Opposite method to “messaging”–also referred to as METI (Messaging the Extraterrestrial Intelligence) - is the Search for Extraterrestrial Intelligence (SETI). SETI uses radio technology to monitor electromagnetic radiation for signs of transmissions from civilizations.

5 Due to copyright restrictions, only a subset of the images on the Golden Record is available for public display. The images that exist on The Golden Record but are copyrighted include Cells and cell division (Turtox/Cambosco), Anatomy (World Book), Human sex organs (Sinauer Associates, Inc.), Conception (Albert Bonniers; Forlag, Stockholm), Group of children (Ruby Mera, UNICEF), Family portrait (Nina Leen, Time, Inc.), Seashore (Dick Smith), Forest scene with mushrooms (Bruce Dale), Leaf (Arthur Herrick), Waterhole (South African Tourist Corp.), Jane Goodall and chimps (Vanne Morris-Goodall), Thailand craftsman (Dean conger), Elephant (Peter Kunstadter), Taj Mahal (David Carroll), Golden Gate Bridge (Ansel Adams), Train (Gordon Gahan), Toronto Airport (George Hunter), Radio telescope (Westerbork, Netherlands, James Blair), Sunset with birds (David Harvey), String Quartet (Quartetto Italiano, Phillips Recordings) amongst other. To preview the publicly available photographs, the reader is invited to visit the NASA JPL website: https://voyager.jpl.nasa.gov/golden-record/whats-on-the-record/images The entire visual contents of the Voyager Message has been published by Sagan in his 1978 book Murmurs of Earth.

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Keywords: NASA, pioneer, golden record, interstellar messages, anthropology of science, voyager

Citation: Capova KA (2021) Introducing Humans to the Extraterrestrials: the Pioneering Missions of the Pioneer and Voyager Probes. Front. Hum. Dyn 3:714616. doi: 10.3389/fhumd.2021.714616

Received: 25 May 2021; Accepted: 13 September 2021; Published: 18 October 2021.

Reviewed by:

Copyright © 2021 Capova. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Klara Anna Capova, [email protected]

This article is part of the Research Topic

Emerging Plurality of Life: Assessing the Questions, Challenges and Opportunities

April 22, 2024

After Months of Gibberish, Voyager 1 Is Communicating Well Again

NASA scientists spent months coaxing the 46-year-old Voyager 1 spacecraft back into healthy communication

By Meghan Bartels

NASA’s Voyager 1 spacecraft is depicted in this artist’s concept traveling through interstellar space, or the space between stars, which it entered in 2012.

NASA/JPL-Caltech

After months of nonsensical transmissions from humanity’s most distant emissary, NASA’s iconic Voyager 1 spacecraft is finally communicating intelligibly with Earth again.

Voyager 1 launched in 1977 , zipped past Jupiter and Saturn within just a few years and has been trekking farther from our sun ever since; the craft crossed into interstellar space in 2012. But in mid-November 2023 Voyager 1’s data transmissions became garbled , sending NASA engineers on a slow quest to troubleshoot the distant spacecraft. Finally, that work has paid off, and NASA has clear information on the probe’s health and status, the agency announced on April 22.

“It’s the most serious issue we’ve had since I’ve been the project manager, and it’s scary because you lose communication with the spacecraft,” said Suzanne Dodd, Voyager project manager at NASA’s Jet Propulsion Laboratory in an interview with Scientific American when the team was still tracking down the issue.

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The Voyager 1 spacecraft is a scientific legend : It discovered that Jupiter’s moon Io, far from being a dead world like our own companion, is instead a supervolcanic world . The craft’s data suggested that Saturn’s moon Titan might have liquid on its surface. And for more than a decade, Voyager 1 has given scientists a glimpse at what space looks like beyond the influence of our sun.

Yet its long years in the harsh environment of space have done a number on the probe, which was designed to last just four years. In particular, degraded performance and low power supplies have forced NASA to turn off six of its 10 instruments, and its communication has gotten even spottier than can be explained by the fact that cosmic mechanics mean a signal takes nearly one Earth day to travel between humans and the probe.

When the latest communications glitch occurred last fall, scientists could still send signals to the distant probe, and they could tell that the spacecraft was operating. But all they got from Voyager 1 was gibberish—what NASA described in December 2023 as “a repeating pattern of ones and zeros.” The team was able to trace the issue back to a part of the spacecraft’s computer system called the flight data subsystem, or FDS, and identified that a particular chip within that system had failed.

Mission personnel couldn’t repair the chip. They were, however, able to break the code held on the failed chip into pieces they could tuck into spare corners of the FDS’s memory, according to NASA. The first such fix was transmitted to Voyager 1 on April 18. With a total distance of 30 billion miles to cross from Earth to the spacecraft and back, the team had to wait nearly two full days for a response from the probe. But on April 20 NASA got confirmation that the initial fix worked. Additional commands to rewrite the rest of the FDS system’s lost code are scheduled for the coming weeks, according to the space agency, including commands that will restore the spacecraft’s ability to send home science data.

Although, for now, Voyager 1 appears to be on the mend, NASA scientists know it won’t last forever. Sooner or later, a glitch they can’t fix will occur, or the spacecraft’s ever dwindling fuel supply will run out for good. Until then NASA is determined to get as much data as possible out of the venerable spacecraft—and its twin, Voyager 2, which experienced its own communications glitch earlier in 2023 .