The moon is a dry and barren place, utterly devoid of life. But has it always been this way? New suggests that perhaps at one point in its history, the moon may have harbored microorganisms similar to those on Earth.
Looking at the moon today, it’s easy to reach the conclusion that it is devoid of life. The moon has no atmosphere, no magnetic field, and what little water it does have is frozen in craters at the poles. It’s hard to think of a place more inhospitable to life, but about 3.5 billion years ago, the moon was a very different place.
In that era, the moon was still relatively new, only about a billion years old. Earth's only natural satellite still had a molten core, and gases escaping from underground magma would have produced an atmosphere. That atmosphere wouldn’t have been as thick as the Earth’s, but it would have been enough to allow liquid water to form on the surface. The molten core could have also generated a magnetic field to protect the lunar surface from solar radiation.
Given these facts, the early moon looks like a potential paradise for microorganisms. And there’s another piece of information that makes the possibility even more likely: life had already developed just 100,000 miles away on Earth. It’s feasible that a stray meteorite could send rocks and bacteria from the surface of Earth to the orbiting moon.
We already know this exchange of meteorites happens between Earth and Mars; scientists have recovered space rocks here on Earth that match those on the Red Planet. These Mars rocks don’t have bacteria on them, but the rocks from Earth just might have. Because meteorites can travel all the way from Mars to the Earth, it’s not hard to imagine rocks from Earth landing on the moon with some bacteria that came along for the ride.
The only way to find out for sure if life has ever existed on the moon is to return there and hunt for clues on the surface. The researchers behind this hypothesis have to collect moon samples and test whether life really could have survived in ancient lunar conditions.