Science fiction has long given the impression that a̳l̳i̳e̳n̳s come from far beyond our own small plot of the universe. But Dr. Abraham “Avi” Loeb, a professor of astronomy at Harvard, believes evidence of e̳x̳t̳r̳a̳t̳e̳r̳r̳e̳s̳t̳r̳i̳a̳l̳ life may be much closer: the moon.
“The moon is interesting for two reasons,” said Loeb. “One, the moon doesn’t have an atmosphere, so anything that impacts the moon will not burn up. Moreover, the moon also doesn’t have geological activity.”
Its surface doesn’t recycle materials the way the Earth’s does, which means anything that has come into contact with it in its lifetime–be it microbial life or single-celled organisms–could remain, in some capacity, on the surface.
“[The moon is] sort of like a mailbox. If we never check that mail, we would never know that we received the message. The message that [e̳x̳t̳r̳a̳t̳e̳r̳r̳e̳s̳t̳r̳i̳a̳l̳ life] exists,” said Loeb. There could potentially be material on the moon that is technological or biological in origin that came from another planetary system.
The moon also presents an easily accessible place to search for such evidence. “We have to remind ourselves that actually going places, going to another star takes a long time. If you use the current rockets that we have and you want to reach the nearest star, it will take 100,000 years,” said Loeb.
If a base could be established on the moon, researchers could create archaeological sites and start looking for evidence. He humorously dubbed this “space archaeology.” Scientists can look at the type and levels of isotopes to identify if a material is from our solar system or interstellar in origin, he explained.
Seth Shostak, a senior astronomer at Search for Extraterrestrial Intelligence Institute, SETI for short, has some reservations about Loeb’s ideas.
“One possibility is that life may have slammed into the moon from some other [planet] but if it was coming from farther away than our own solar system, it becomes very difficult,” said Shostak.
Biological organisms may simply be unable to survive the harshness of space in their journey across the universe to the moon, explained Shostak. “The desiccation, all the water would either be frozen or just escape as gas from the rock.”
Then there’s the space radiation, which would break organisms apart even more. “These little microbes don’t have life jackets,” he said. As a result, the evidence of e̳x̳t̳r̳a̳t̳e̳r̳r̳e̳s̳t̳r̳i̳a̳l̳ life within an interstellar body such as a meteor would be destroyed and wouldn’t survive its travel to the moon.
In response to Shostak’s doubts, Loeb discussed the possibility of life being protected in the core of a large enough meteor.
“It’s true that there is a lot of hazards out in interstellar space. For example, cosmic ray damage, biological material, and so forth,” said Loeb. “But, if you think about a rock that arrives from a distance from a remote planetary system, if it’s big enough, the interior will be protected.”
MIT researchers have looked into how much a Martian rock heats when it enters Earth’s atmosphere. Loeb takes their conclusions as evidence that long distance travel across space may be possible for microbes hidden away at the center of meteors or asteroids.
“The conclusion was that the [interior] of the rock was not heated by more than 40 degrees Celsius, which means that any biological life could have survived,” said Loeb. “We know that a rock could have carried biological life from Mars and survived the impact. So, we shouldn’t exclude the possibility that the moon might have some.”
Shostak is still unsure of the merits of Loeb’s theory given that at this time, there is no evidence to say one way or the other.
“I think it’s good that he stimulates some thought on these things,” said Shostak. “On the other hand, you know, we’ve also got almost nothing on the moon. So, we don’t really know.”
Both Loeb and Shostak do agree on one thing: scientists need to keep their minds open and not shut down seemingly implausible theories.
“It’s the mistake that is often done in science where people decide ahead of time what they might find,” said Loeb. “The problem with that approach is that it may save you time but you will never discover anything new because you basically put blinders on.”
In September 2019, NASA announced a project to return American astronauts to the moon. Loeb hopes that in future expeditions, research can be done on the surface composition in the hunt for evidence of e̳x̳t̳r̳a̳t̳e̳r̳r̳e̳s̳t̳r̳i̳a̳l̳ life.
NASA hopes to establish sustainable missions in order to fully research the moon’s surface and eventually use the base as a launching point to get to Mars by 2024.
“There are several examples of frontiers that I worked on, promoted, that ended up being successful,” said Loeb. “Before the first discovery, people were extremely skeptical and made very demeaning remarks. I’ve seen it and obviously I see it right now in the search for life. So to me, this is a signature of a field that is ripe for a breakthrough.”