Water on the Moon may be much more common than previously thought, according to a new study by Jessica Barnes from the Open University in the U.K. and her co-authors. This is a sharp turnaround in our thinking following the Apollo missions, which led scientists to conclude that the rocks on the Moon are bone dry.
The Moon has been pummeled by asteroids and comets ever since it formed from a collision with the proto-Earth billions of years ago. The new research by Barnes reveals that many of the objects that have struck the Moon have been carbonaceous chondrites, which are rich in water and organic compounds. These rocks would not have found fertile ground on the Moon as they did on Earth, where they likely provided the building blocks for the origin of life. Nevertheless, the billions of tons of frozen water locked up deep inside lunar craters may hold secrets about the evolution of terrestrial life. In fact, only on the Moon can we find such evidence, because on Earth it’s been all but erased by millennia of weathering and tectonic activity.
As many asteroids and comets as struck the Moon in its early history, even more must have collided with Earth, due to its larger size. If the collision was energetic enough, some material from Earth’s surface would have been ejected with enough velocity to reach space and eventually the Moon, where it would have been deposited around the same time that life arose on Earth. If the ejected material was buried deep enough, it would have been protected from cosmic radiation, which means it may still contain evidence from the time when life originated on our planet. Here we could possibly find the first ancient cells before they used DNA to pass on genetic information. Or perhaps we might even find evidence of early life experimenting with a different biochemistry.
If we ever mine the ice-rock mixtures at the lunar South Pole, like the ones that exist in Shackleton Crater—perhaps to produce drinking water for the astronauts at a future lunar station—let’s not forget to look for clues related to ancient life on Earth.