The Pioneer Plaque impact

The Pioneer Plaque impact

In Carl Sagan’s publication Cosmic Connection (1975) he reveals some of the background and impact of the design of the Pioneer 10 and 11 plaque. Below we publish some excerpts from this publication.

Carl Edward Sagan (1934 – 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. His best known scientific contribution is research on extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation.

Carl Sagan (1934-1996)

He spent most of his career as a professor of astronomy at Cornell University, where he directed the Laboratory for Planetary Studies. Sagan was associated with the U.S. space program from its inception. From the 1950s onward, he worked as an advisor to NASA, where one of his duties included briefing the Apollo astronauts before their flights to the Moon. Sagan contributed to many of the robotic spacecraft missions that explored the Solar System, arranging experiments on many of the expeditions.
Sagan’s contributions were central to the discovery of the high surface temperatures of the planet Venus. In the early 1960s no one knew for certain the basic conditions of Venus’ surface, and Sagan listed the possibilities in a report later depicted for popularization in a Time Life book Planets. His own view was that Venus was dry and very hot as opposed to the balmy paradise others had imagined. He had investigated radio waves from Venus and concluded that there was a surface temperature of 500 °C (900 °F). As a visiting scientist to NASA’s Jet Propulsion Laboratory, he contributed to the first Mariner missions to Venus, working on the design and management of the project. Mariner 2 confirmed his conclusions on the surface conditions of Venus in 1962.

Sagan on UFO’s

In 1947, the year that inaugurated the “flying saucer” craze, the young Sagan suspected the “discs” might be alien spaceships.

Sagan’s interest in UFO reports prompted him on August 3, 1952, to write a letter to U.S. Secretary of State Dean Acheson to ask how the United States would respond if flying saucers turned out to be extraterrestrial. He later had several conversations on the subject in 1964 with Jacques Vallée1. Though quite skeptical of any extraordinary answer to the UFO question, Sagan thought scientists should study the phenomenon, at least because there was widespread public interest in UFO reports.

Stuart Appelle2 notes that Sagan “wrote frequently on what he perceived as the logical and empirical fallacies regarding UFOs and the abduction experience. Sagan rejected an extraterrestrial explanation for the phenomenon but felt there were both empirical and pedagogical benefits for examining UFO reports and that the subject was, therefore, a legitimate topic of study.”

Review Project Blue Book

In 1966 Sagan was a member of the Ad Hoc Committee to Review Project Blue Book, the U.S. Air Force’s UFO investigation project. The committee concluded Blue Book had been lacking as a scientific study, and recommended a university-based project to give the UFO phenomenon closer scientific scrutiny. The result was the Condon Committee (1966–68), led by physicist Edward Condon3, and in their final report they formally concluded that UFOs, regardless of what any of them actually were, did not behave in a manner consistent with a threat to national security.

Sociologist Ron Westrum writes that “The high point of Sagan’s treatment of the UFO question was the AAAS’ symposium in 1969. A wide range of educated opinions on the subject were offered by participants, including not only proponents such as James McDonald and J. Allen Hynek but also skeptics like astronomers William Hartmann and Donald Menzel. The roster of speakers was balanced, and it is to Sagan’s credit that this event was presented in spite of pressure from Edward Condon.” With physicist Thornton Page, Sagan edited the lectures and discussions given at the symposium; these were published in 1972 as UFO’s: A Scientific Debate. Some of Sagan’s many books examine UFOs (as did one episode of TV Series Cosmos) and he claimed a religious undercurrent to the phenomenon.

Sagan again revealed his views on interstellar travel in his 1980 Cosmos series. In one of his last written works, Sagan argued that the chances of extraterrestrial spacecraft visiting Earth are vanishingly small. However, Sagan did think it plausible that Cold War concerns contributed to governments misleading their citizens about UFOs, and wrote that “some UFO reports and analyses, and perhaps voluminous files, have been made inaccessible to the public which pays the bills … It’s time for the files to be declassified and made generally available.” He cautioned against jumping to conclusions about suppressed UFO data and stressed that there was no strong evidence that aliens were visiting the Earth either in the past or present.

Sagan briefly served as an adviser on Stanley Kubrick’s film 2001: A Space Odyssey. Sagan proposed that the film suggest, rather than depict, extraterrestrial superintelligence.

After suffering from myelodysplasia, Sagan died of pneumonia at the age of 62.

A message to Earth

The golden greeting card placed aboard the Pioneer 10 and 11 spacecraft was intended for the remote contingency that representatives of an advanced extraterrestrial civilization, some time in the distant future, might encounter this first artifact of mankind to leave the Solar System. But the message has had a more immediate impact. It has already been meticulously studied – not by extraterrestrials, but by terrestrials. Human beings all over the planet Earth have examined the message, applauded it, criticized it, interpreted it, and proposed alternative messages.

The graphics of the message have been reproduced widely in newspapers and television programs, small art and literary magazines, and national newsweeklies. We (Carl Sagan) have received letters from scientists and housewives, historians and artists, feminists and homosexuals, military and foreign service officers, and one professor of bass fiddle. Our plaque has been reproduced for commercial sale by an engraving company, a distributor of scientific knickknacks, a manufacturer of tapestry, and an Italian mint specializing in silver ingots – all, incidentally, without authorization.

Pioneer plaque

Tears of joy

The great majority of comments have been favorable, some extraordinarily enthusiastic. One scientist writes to say that the description of the scientific basis of the plaque we published in the American journal Science was the first scientific paper he had ever read that moved him to tears of joy. A correspondent in Athens, Georgia, writes, “We’ll all be gone before this particular message in a bottle is picked up by some indescribable spacecomber; nevertheless, its very existence, the audacity of the dream, inevitably produces in me – and many others I know – the feelings of a Balboa, a Leeuwenhoek, a human being being human!

But there were also critical comments. They were not directed at the pulsar map, which was the scientific heart of the message, but rather at the representation of the man and the woman. The original drawings of this couple were made by my (Carl Sagan’s) wife and were based upon the classical models of Greek sculpture and the drawings of Leonardo da Vinci. We do not think this man and woman are ignoring each other. They are not shown holding hands lest the
extraterrestrial recipients believe that the couple is one organism joined at the fingertips. (E.g. in the absence of indigenous horses, both the Aztecs and the Incas interpreted the mounted conquistador as one animal – a kind of two-headed centaur.)

Sign of good will

The man and woman are not shown in precisely the same position so that the suppleness of the limbs could be communicated – although we well understand that the conventions of perspective and line drawing popular on Earth may not be readily apparent to civilizations with other artistic conventions.
The man’s right hand is raised in what I once read in an anthropology book is a “universal” sign of good will – although any literal universality is of course unlikely. At least the greeting displays our opposable thumbs. Only one of the two people is shown with hand raised in greeting, lest the recipients deduce erroneously that one of our arms is bent permanently at the elbow.

Feminine criticism

Several women correspondents complain that the woman appears too passive. One writes that she also wishes to greet the universe, with both arms outstretched in womanly salutation. The principal feminine criticism is that the woman is
drawn incomplete – that is, without any hint of external genitalia. The decision to omit a very short line in this diagram was made partly because conventional representation in Greek statuary omits it. But there was another reason: our desire to see the message successfully launched on Pioneer 10. In retrospect, we may have judged NASA’s scientific-political hierarchy as more puritanical than it is. In the many discussions that I held with such officials, up to the Administrator of the National Aeronautics and Space Administration and the President’s Science Adviser, not one Victorian demurrer was ever voiced; and a great deal of helpful encouragement was given.

Yet it is clear that at least some individuals were offended even by the existing representation. The Chicago Sun Times, for example, published three versions of the plaque in different editions all on the same day: In the first the man was
represented whole; in the second, suffering from an awkward and botched airbrush castration; and in the final version – intended no doubt to reassure the family man dashing home – with no sexual apparatus at all. This may have pleased
one feminist correspondent who wrote to the New York Times that she was so enraged at the incomplete representation of the woman that she had an irresistible urge “to cut off the man’s … right arm!

Community standards

The Philadelphia Inquirer published on its front page an illustration of the plaque, but with the nipples of the woman and the genitalia of the man removed. The assistant managing editor was quoted as saying, “A family newspaper must
uphold community standards
An entire mythology has evolved about the absence of discernible female genitalia. It was a column by the respected science writer Tom O’Toole, of the Washington Post, that first reported that NASA officials had censored an original depiction of the woman. This tale was then circulated in nationally syndicated columns by Art Hoppe, Jack Stapleton Jr., and others. Stapleton imagined the enraged citizens of another planet receiving the plaque, and in a paroxysm of moral outrage covering over with adhesive tape the pornographic representation of the feet of the man and the woman. One letter writer to the Washington Daily News proposed that if the woman was to be censored, then for consistency the noses of the humans should have been painted blue.

A tut-tutting letter in Playboy magazine complained about this further intrusion of government censorship, already quite bad enough, into the lives of the citizenry. Editorials in sciencefiction magazines also took the government to task. The idea of government censorship of the Pioneer 10 plaque is now so well documented and firmly entrenched that no statement from the designers of the plaque to the contrary can play any role in influencing the prevailing opinion. But we can at least try.


What sexuality there is in the message also drew epistolary fire. The Los Angeles Times published a letter from an irate reader that went: “I must say I was shocked by the blatant display of both male and female sex organs on the front page of the Times. Surely this type of sexual exploitation is below the standards our community has come to expect from the Times. Isn’t it enough that we must tolerate the bombardment of pornography through the media of film and smut magazines? Isn’t it bad enough that our own space agency officials have found it necessary to spread this filth even beyond our own solar system?”
This was followed several days later by another letter in the Times: “I certainly agree with those people who are protesting our sending those dirty pictures of naked people out into space. I think the way it should have been done would have been to visually bleep out the reproductive organs of the drawings of the man and the woman. Next to them should have been a picture of a stork carrying a little bundle from heaven. Then if we really want our celestial neighbors to know how far we have progressed intellectually, we should have included pictures of Santa Claus, the Easter Bunny, and the Tooth Fairy.
The New York Daily News headlined the story in typical fashion: “Nudes and Map tell about Earth to Other Worlds.”

Some correspondents argue that the function of the sexual organs would not be obvious even had they been graphically displayed, and urged on us a sequence of cartoons from copulation to birth to puberty to copulation. There was not quite room for this on a 6-inch by 9-inch plaque. I can also imagine the letters that would then have been written to the Los Angeles Times.
An article in Catholic Review criticizes the plaque because it “includes everything but God,” and suggests that, rather than a pair of human beings, it would have been better to have borne a sketch of a pair of praying hands.
Another correspondent maintains that the perspective conventions are insuperably difficult, and urges us to send the complete cadavers of a man and a woman. They would be perfectly preserved in the cold of space, and could be
examined by extraterrestrials in detail. We declined on grounds of excess weight.
The front page of the Berkeley, California, Barb, apparently intending to convey an impression that the man and woman on the message were too straight, reproduced them with the caption, “Hello. We’re from Orange County.
This comment touches on an aspect of the representation of the man and woman that I personally feel much worse about, although it has received almost no other public notice. In the original sketches from which the engravings were
made, we made a conscious attempt to have the man and woman panracial.


The woman was given epicanthian folds and in other ways a partially Asian appearance. The man was given a broad nose, thick lips, and a short “Afro” haircut. Caucasian features were also present in both. We had hoped to represent at least three of the major races of mankind. The epicanthian folds, the lips, and the nose have survived into the final engraving. But because the woman’s hair is drawn only in outline, it appears to many viewers as blond, thereby destroying the possibility of a significant contribution from an Asian gene pool. Also, somewhere in the transcription from the original sketch drawing to the final engraving the Afro was transmuted into a very non-African Mediterranean-curly haircut. Nevertheless, the man and woman on the plaque are, to a significant degree, representative of the sexes and races of mankind.

Galactic language

There is, of course, the possibility that the message on Pioneer 10 and 11 – invented by human beings but directed at creatures of a very different kind – may prove ultimately mysterious to them. We think not. We think we have written the message – except for the man and woman – in a universal language. The extraterrestrials cannot possibly understand English or Russian or Chinese or Esperanto, but they must share with us common mathematics and physics and astronomy. I believe that they will understand, with no very great effort, this message written in the galactic language: “Scientific.”

Challenge to us

Perhaps the most perceptive editorial comment is the New York Times‘: “… that gold-plated plaque is more of a challenge to us. Despite the uncanny mastery of celestial laws that permits man to shoot his artifacts at the stars, we find ourselves still depressingly inept at ordering our own systems here on Earth. Even as we try to find a way to insure that sapient man will not consume his planet in nuclear fires, a rising chorus warns us that man may very well exhaust his earth either by overbreeding or by inordinate demands on its resources, or both. So the marker launched into space is at the same time a gauntlet thrown down to earth: That the gold-plated plaque convey in its time the message that man is still here – not that he had been here.

1 Vallée is an important figure in the study of unidentified flying objects (UFOs), first noted for a defense of the scientific legitimacy of the extraterrestrial hypothesis and later for promoting the interdimensional hypothesis.

2 Apelle was a professor and writer, with an interest in topics dealing with anomalous perception, including hypnotic experience, and reports of unidentified flying objects and alien abduction.

3 Condon became widely known in 1968 as principal author of the Condon Report, an official review funded by the United States Air Force that concluded that unidentified flying objects (UFOs) have prosaic explanations.
The lunar crater Condon is named for him.

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