The Pioneer plaques are a pair of aluminum plaques which were placed on board the Pioneer 10 and Pioneer 11 Spacecraft, featuring a pictorial message from humanity, in case either Pioneer 10 or 11 are intercepted by extraterrestrial beings. The plaques show the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft.
The Pioneer spacecraft were the first human-built objects to leave the solar system. The plaque is attached to the antenna support struts in a position that shields it from erosion by stellar dust.
The Voyager Golden Record, a much more complex and detailed message using (then) state-of-the-art media, was attached to the Voyager spacecraft launched in 1977.
The original idea, that the Pioneer spacecraft should carry a message from mankind, was first mentioned by Eric Burgess when he visited the Jet Propulsion Laboratory in Pasadena California during the Mariner 9 mission. Together with Richard Hoagland, he approached Dr. Carl Sagan, who had lectured about communication with extraterrestrial intelligences at a conference in Crimea.
Dr. Sagan was enthusiastic about the idea of sending a message with the Pioneer spacecraft. NASA agreed to the plan and gave him three weeks to prepare a message. Together with Dr. Frank Drake he designed the plaque, and the artwork was prepared by Sagan's then wife Linda Salzman Sagan.
The first plaque was launched with Pioneer 10 on March 2, 1972, and the second followed with Pioneer 11 on April 5, 1973. Both spacecraft left the solar system in the 1980s.