Aldrin and Armstrong blasted off from the Moon in the Eagle lander at 17:54 UTC on 21st June, after spending 21 hours and 36 minutes on the lunar surface. They were carrying 22 kilograms of samples, including 50 rocks, fine-grained lunar “soil” and two core tubes that included material from up to 13 centimetres below the Moon’s surface.

They left behind the American flag that they had planted on the Moon, but as it had only been placed about 8 metres from Eagle, it was blown over during the ascent. Future Apollo missions would learn from this mistake, and plant their flags further away.

Buzz Aldrin salutes the first American flag erected on the Moon
[Image credit: NASA / Neil A. Armstrong]

They also left an Apollo 1 mission patch, as a memorial to the three astronauts who died in a launchpad accident, and two medals awarded to Russian cosmonauts Yuri Gagarin and Vladimir Komarov, which had been passed to the Apollo 11 crew by American astronaut Frank Borman, after he was given them by the cosmonauts’ widows. And a small silicon disc, containing miniaturised goodwill messages from 73 countries, and the names of congressional and NASA leaders, also stayed behind.

On top of that, they left a golden olive branch, and there’s one on the official mission patch, too. The use of a symbolic olive branch dates back to ancient Greece. In Greek mythology, Poseidon and Athena were vying for possession of Athens. Poseidon walloped the Acropolis with his trident, so that a salt water well sprang forth. Athena planted the first olive tree by the well, and since this was considered the better gift, the city became hers. Olive wreaths were worn by brides, and awarded to Olympic victors.

Apollo 11 mission patch
[Image credit: NASA]

The Roman poet Virgil associated the olive with the goddess Pax and used the olive branch as a symbol of peace in his work. Pax Romana envoys from the Roman Empire used olive branches as tokens of peace, and the olive branch has become a symbol of peace throughout the world.

Eagle’s ascent engine had never been tested on Moon, and no one was 100% confident that it would get the astronauts back into space and safely docked with the command module. Privately, the astronauts estimated the odds at around 50/50, but they went anyway. So one of the things they did before they left was to jettison everything from the lunar module that they wouldn’t need on the way home, to reduce weight and increase their chances. They left behind all kinds of junk, including the Passive Seismic Experiment, which used seismic readings from meteoroid impacts to map the inner structure of the Moon, a laser reflector that helped measure the precise distance from the Earth to the Moon, an assortment of tongs, sample scoops and scales, a hammer and various containers and brackets.

A ‘jett’ (jettison) bag, tossed onto the Moon from Eagle
[Image credit: NASA]

The “Toss Zone” is an arc of discarded space litter, to the west of the landing site. It also contains two pairs of discarded lunar overshoes, two portable life support systems, and a couple of empty food bags. The Lunar Legacy Project at New Mexico State University has a detailed list of everything the crew left behind, complete with a map. There’s also an official NASA catalogue of “manmade material on the Moon”, which includes lunar landers as well as Apollo trash.

In total the 12 people who have stepped on the Moon have left behind 96 bags human waste bags, although some of them were discarded unused. As such, we have taken microbial life from Earth, and stranded it in one of the most extreme environments imaginable. The human waste we left behind has become an unintended experiment on whether microbial life could survive on the Moon, so astrobiologists really want to get it back and see what has happened to it in the intervening fifty years! Retrieving some samples may tell us about the extreme conditions life can endure, as well as the potential for contaminating — or even seeding life on — moons and planets we explore.