The moon, the Earth’s sole natural satellite, is full of mysteries. Orbiting at 385,000 km and barely 1.2 percent the mass of the Earth, the moon has fascinated humans for centuries. In 1969, the first humans landed on the moon, but still today our knowledge of it remains limited. As we continue to look for life elsewhere in the Universe, one question remains: could there be life on the moon?
When talking about life on the moon no need to think that there could exist any form of life — at least as we know it — on the surface of the moon, the absence of atmosphere prohibiting the presence of liquid water. Indeed, if you pour water on the moon, it will evaporate or solidify instantly.
The Moon, however, would have ice at the bottom of some craters. We are not talking here about a giant floe like at the poles of our planet but frozen water, mixed with regolith, this layer of dust 10 m thick that covers the lunar ground. This water would come from the fall of meteorites and comets billions of years ago. In the polar cold at the bottom of the craters where the temperatures are around -230 °C, this ice can be preserved forever.
But if the moon is partly formed of earthy elements — we do not know 100% its origin but it is likely that it was formed after the Earth’s collision with Thea, a planet the size of Mars — it should in theory also possess water and organic molecules, the elemental bricks of life.
There may be pockets of liquid water in the lunar subsoil. While the subsoil is a real permafrost, frozen at 2 m depth at -17 °C, as we go lower, the temperature increases by about 1.75 ° per meter of depth. Underground water could also be kept liquid by underground friction.
If there are pockets of liquid water under the lunar soil, they most likely have been there for billions of years, which is enough time for life to appear and possibly evolve in more complex form. However, even if life does exist in those water packets, it still very unlikely that they would have an ecosystem of a wealth comparable to that on Earth.
Until we go back to the moon, and take viable samples to test for microbial traces of life, the response to the question of whether there is life on the moon will be: unlikely but maybe.