Pioneer 10 and 11 were spacecraft developed by NASA and lanuched in 1972. Its mission is to study Jupiter and maybe come into contact with extraterrestrial beings. They carried the Pioneer plaques, a pair of metallic plaques with a drawing on them. The plaques were created so that, if intercepted by any aliens, it could guide them to Earth.
The plaque depicts two hydrogen atoms in hyperfine transition and a drawing of a man and a woman without clothes, so the aliens understand who sent the probe. The man holds his hand up as a sign of peace. A drawing of the probe is in the background, to clarify the builders of Pioneer 10. There is also a map of the sun's position relative to 14 pulsars, rapidly rotating neutron stars.
A drawing of the Solar system is at the bottom, depicting the Sun and the nine planets. Another drawing of the probe points to Earth, so extraterrestrials will understand that the Pioneer 10 came from the third planet, Earth.