By Morris Jones
2019 marks the fiftieth anniversary of the mission of Apollo 11, when humans walked on another world for the first time. While the flight was a tremendous achievement for science, technology and exploration, there's one aspect that's rarely discussed. In some ways, Apollo 11 was a proto-project for METI.
The Lunar Module that carried Neil Armstrong and Buzz Aldrin to the surface of the Moon contained a small metal plaque as a history marker. "HERE MEN FROM THE PLANET EARTH FIRST SET FOOT UPON THE MOON JULY 1969, A. D. WE CAME IN PEACE FOR ALL MANKIND." The signatures and names of astronauts Neil Armstrong, Michael Collins and Edwin (Buzz) Aldrin were included, along with those of US President Richard Nixon. Two hemispherical maps of Earth were also included. The plaque was attached to a landing leg of the Lunar Module, and remained behind when the astronauts departed.
This plaque was mainly intended as a historical marker for the benefit of other humans, possibly astro-archeologists who may return to the Moon at some time. But the message could also be seen as a tacit signal to other civilizations that could one day visit our solar system. Admittedly, it does not attempt to describe planet Earth and the human race with as much detail as a dedicated METI message, but it's still useful. A widely-spoken native language of humans is on display. The nature of the spacecraft and its mission is recorded. Some idea of how we record events and sites for posterity is contained. Admittedly, it would be hard for an extraterrestrial visitor to decode all of this without more background information, but that could possibly be obtained from other human artefacts and signals.
The astronauts left some other clues behind. Micro-etching was used to engrave greetings from various states on a small token. A small copy of the Bible was also left on the Moon. Again, this is not METI as we usually know it, but it still gives information on humanity.
Similar plaques were carried by the other Apollo Moon missions. These usually contained the name of the mission, the names of the astronauts, the date of the mission and the name of the Lunar Module, alongside the two-hemisphere depiction of Earth. But Apollo 17 was the final mission to land on the Moon, and carried a more substantial message. "HERE MAN COMPLETED HIS FIRST EXPLORATIONS OF THE MOON DECEMBER 1972, A. D. MAY THE SPIRIT OF PEACE IN WHICH WE CAME BE REFLECTED IN THE LIVES OF ALL MANKIND."
It's more likely that the next intelligent lifeforms to visit these plaques will be humans rather than extraterrestrials. But if human civilization should fall, they could be memorials to our existence. At some point, they could ensure that the rest of the universe knows of us, and will not forget us.