When signals from the two Pioneers can no longer be received at Earth, they will have another mission as they continue into interstellar space. This final mission began when, in a high vacuum, Pioneer 10 gleamed under the harsh lights of an artificial sun in the space simulator at TRW Systems, California. The final test was underway before the spacecraft was to be shipped to Kennedy Space Center. A group of science correspondents from the national press were at TRW Systems for a briefing on Pioneer and had been invited to see the spacecraft under test.
Looking at Pioneer through the portholes of the simulator, one of the correspondents, Eric Burgess, then with The Christian Science Monitor, visualized Pioneer 10 as mankind's first emissary beyond our Solar System. This spacecraft should carry a special message from mankind, he thought, a message that would tell any finder of the spacecraft a million or even a billion years hence that planet Earth had evolved an intelligent species that could think beyond its own time and beyond its own Solar System.
He mentioned this idea to Richard Hoagland, a freelance writer, and to Don Bane, then with the Los Angeles Herald-Examiner, and they enthusiastically agreed. The result was that Burgess and Hoagland approached Dr. Carl Sagan, Director of the Laboratory of Planetary Studies, Cornell University, who was then visiting the Jet Propulsion Laboratory, Pasadena, in connection with Mariner 9's mission to Mars. A short while earlier, Dr. Sagan had been involved in a conference in the Crimea devoted to the problems of communicating with extraterrestrial intelligences and, together with Dr. Frank Drake, Director of the National Astronomy and Ionosphere Center, Cornell University, had designed one type of message that might be used to communicate with an alien intelligence.
Dr. Sagan was enthusiastic about the idea of a message on the Pioneer spacecraft. He and Dr. Drake designed a plaque, and Linda Salzman Sagan prepared the artwork. The design was presented to the National Aeronautics and Space Administration; they accepted it for this first Pioneer from our Solar System into the Galaxy.
The plaque design was etched into a gold- anodized aluminum plate 15.25 by 22.8 cm (6 by 9 in.) and 0.127 cm (0.05 in.) thick. This plate was attached to the antenna support struts of the spacecraft in a position where it would be shielded from erosion by interstellar dust [illustration].
When Pioneer 10 flew by Jupiter, the spacecraft acquired sufficient kinetic energy to carry it completely out of our Solar System. In about 100,000 years, it will have coasted to the distance of the nearest star, in the direction of the constellation Taurus. Sometime, perhaps many billions of years from now, it may pass through the planetary system of a remote stellar neighbor, one of whose planets may have evolved intelligent life.
If that life possesses sufficient capability to detect the Pioneer spacecraft - needing a higher technology than mankind possesses today - it may also have the curiosity and the technical ability to pick up the spacecraft and take it into a laboratory to inspect it. Then the plaque with its message from Earth should be found and possibly deciphered.