Pioneer 10 is (perhaps, was?) a space probe launched by NASA in 1972 pointed towards Jupiter. The first part of its mission was to photograph the surface from space and study its immediate environment, the asteroid belt, the solar wind, and cosmic rays. On successfully completing this first part of its mission, Pioneer 10 used its orbit around the giant planet to slingshot beyond it, becoming the first human-made object to achieve the escape velocity required to leave the Solar System.
Radio communications were lost January 23, 2003 when electric power for its transmitter stopped. The probe was then nearly 12 billion kilometers from Earth. It must be further now. Here’s an artist’s impression.
Pioneer 10 had another, slightly below-the-radar, mission which involved a single piece of precious cargo—one 6 × 9 inch gold-anodized aluminum plaque bolted onto the frame of the satellite. The plaque was the work of Carl Sagan, a Cornell astrophysicist, Linda Salzman Sagan, an artist, and Frank Drake, an astronomer who later instigated the Arecibo message.
The original idea for the plaque came from Eric Burgess, a British journalist visiting the Jet Propulsion Laboratory in Pasadena, California. After being briefed on the mission plan for Pioneer 10, he reasoned that if NASA was going to attempt to launch the first human-made object out of our solar system, then it was possible that the probe might eventually be found somewhere else, and perhaps by extraterrestrial life forms. He dreamed up a cosmic message-in-a-bottle which would carry fundamental information about humans on Earth for the plaque’s extra-solar recipients.
Sagan was already working around and lecturing on alien communication, and he was invited to head up the effort. He was relatively young, charismatic, and had an exceptional ability to communicate complex astrophysical ideas in a direct fashion.
He went on to co-write and narrate a multi-part public television series, Cosmos, which made a big impression on me in my youth. He is magnetic onscreen, portraying a cocktail of wonder and skepticism that he would later insist was the key to doing good science; if you have not seen it, you really ought to. Here he is unpacking the 4th dimension.
The Pioneer 10 plaque is a densely coded graphic object, consisting of at four primary zones of information. At the top to the left, is a drawing which conveys the transition of a Hydrogen atom. The time and distance implied provides a standard unit which becomes a key for reading measures in the other graphics. Below that is a misshapen asterisk which conveys where in the universe this plaque originated by identifying Earth's coordinates using radio pulsar distances. To the right of that is a drawing of two humans which is not anatomically correct. And along the bottom is diagram of our solar system showing the path on which the satellite left. It is almost impossibly dense, and perhaps that makes sense given its ambitions. This first piece of interstellar graphic design is likely somewhere at least 7.6 billion miles away by now.
Here is Carl Sagan around 1972 holding the completed Pioneer 10 plaque: