Image by "T"eresa via FlickrTwenty-seven years ago this week, Pioneer 10 became the first man-made object to "leave" the solar system when it passed orbit of Neptune on June 13, 1983. Technically, Pioneer 10 has yet to enter the Oort cloud, let alone escape the heliopause, so it's not beyond the influence of our sun. Nonetheless, Pioneer 10 is the first man-made object to carry a tangible human message outside the local planetary system -- the first Pioneer Plaque.
Designed by Carl "Contact & Cosmos" Sagan and Frank "The Drake Equation" Drake, the Pioneer Plaque contained a supposedly universally comprehensible description of the Pioneer probe's origins, including mathematic and astronomic directions to our solar system and a basic depiction of human beings. The depiction of humanity included simplified nude line drawings of an adult human male and female. While Stephen Hawking has of late suggested that we should not tell aliens where we live, the big controversy about extraterrestrial communications in 1972 was that we launched nudie pictures into space.
Thus, while an identical Pioneer Plaque was launched on Pioneer 11 in 1973, the Voyager Golden Records attached to Voyagers 1 and 2 omitted the nude drawings. In fact, Sagan was able to reuse only two items from the Pioneer Plaques when he designed the Voyager Golden Records in 1977.
What were the only two items displayed on both Pioneer Plaques and Voyager Records?
The only two pictograms to appear on every tangible message humans have sent into interplanetary space are a diagram of the hyperfine transition of neutral hydrogen (to show how we use two-dimensional images to represent the most basic states of the most abundant element in the universe) and a pulsar map that shows the location of our sun (to direct alien overlords to the the newest vassal state of the Galactic Empire).
The depiction of of our solar system, the notation of Pioneer probe's course, and -- naturally -- the nude drawings of human adults were all tossed aside when it came time to create the Voyager Records. Ironically, the Voyager Golden Records contain more explicit sexual content than the Pioneer Plaques, including a diagram of human sexual reproduction and images of human sex organs, but those images are encoded into the record itself, rather than visibly etched upon it. The Chicago Sun-Times apocryphally retouched its photos of the Pioneer Plaques to omit the male and female genitalia; the Voyager Golden Records spared them the exercise.
That may be a cosmic morality tale of excess prudery -- nude images are okay for Proxima Centauri, but they won't play in Peoria -- but it's another fine example of the Truly Trivial.