Science fiction has long given the impression that aliens come from far beyond our little patch of the universe. But Dr. Abraham “Avi” Loeb, a professor of astronomy at Harvard, believes evidence of extraterrestrial life may be much closer: the Moon.
“The moon is interesting for two reasons,” Loeb said. “One, the moon doesn’t have an atmosphere, so anything that hits the moon won’t burn up. In addition, the moon also has no geological activity.
Its surface doesn’t recycle materials like Earth’s does, which means that anything that has been in contact with it during its lifetime – be it microbial life or single-celled organisms – could remain, to some extent, on the surface.
“[The moon is] kind of like a mailbox. If we never check that email, we will never know we received the message. The message that [extraterrestrial life] exists,” Loeb said. There could be on the Moon material of technological or biological origin from another planetary system.
The moon also presents an easily accessible place to search for such evidence. “We have to remember that actually going to another place, going to another star, takes a long time. If we use today’s rockets and we want to get to the nearest star, it will take 100,000 years,” Loeb said.
If a base could be established on the Moon, researchers could create archaeological sites and start looking for evidence. He humorously dubbed it “spatial archaeology.” Scientists can look at the type and levels of isotopes to identify whether a material is from our solar system or interstellar in origin, he explained.
Seth Shostak, a senior astronomer at the Search for Extraterrestrial Intelligence Institute, SETI, has some reservations about Loeb’s ideas.
“One possibility is that life has collided with the moon from some other [planet] but if it came from further away than our own solar system, it becomes very difficult,” Shostak said.
Biological organisms might simply be unable to survive the harshness of space on their journey across the universe to the Moon, Shostak explained. “Drying out, all the water would either freeze or just escape as gas from the rock.”
Then there is space radiation, which would further break down organisms. “These little microbes don’t have life jackets,” he said. As a result, evidence of extraterrestrial life within an interstellar body such as a meteorite would be destroyed and would not survive its journey to the Moon.
In response to Shostak’s doubts, Loeb discussed the possibility that life was protected in the core of a sufficiently large meteorite.
“It is true that there are many dangers in interstellar space. For example, damage from cosmic rays, biological material, etc,” Loeb said. “But, if you think of a rock coming in from a distance from a remote planetary system, if it’s big enough, the interior will be protected.”
MIT researchers have analyzed how much a Martian rock heats up when it enters the Earth’s atmosphere. Loeb sees his conclusions as proof that long-distance travel through space may be possible for microbes hiding in the center of meteorites or asteroids.
“The conclusion was that the [interior] of the rock did not get warmer than 40 degrees Celsius, which means that any biological life could have survived,” Loeb said. “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 something.”
Shostak is still unsure of the merits of Loeb’s theory, given that there is currently no evidence to say one way or the other.
“I think it’s good that it stimulates reflection on these things,” Shostak said. “On the other hand, you know, we also have almost nothing on the moon. So we don’t really know.”
Both Loeb and Shostak agree on one thing: Scientists must keep an open mind and not shut down seemingly implausible theories.
“It’s the mistake that’s often made in science, where people decide in advance what they might find,” Loeb said. “The problem with that approach is that it may save you time but you’ll never discover anything new because you’re basically putting on blinders.”
In September 2019, NASA announced a project to return American astronauts to the Moon. Loeb hopes that future expeditions will be able to investigate the composition of the surface in search of evidence of extraterrestrial life.
NASA hopes to establish sustainable missions to thoroughly investigate the lunar surface and eventually use the base as a launch point to reach Mars in 2024.
“There are several examples of borders that I worked on, promoted, that ended up being successful,” Loeb said. “Before the first discovery, people were extremely skeptical and made very derogatory comments. I have seen it and obviously I see it right now in the search for life. So, to me, this is the signature of a field that is ripe for a breakthrough.”