We know there's water frozen on the Moon — and we now know there's plenty more water elsewhere in the solar system . So how did it all get there? It might well be the Sun that's behind it all.
That's the conclusion of a new study from researchers at the University of Michigan, University of Tennessee, and the California Institute of Technology. We know water and its associated compounds is found not only in the Moon's hidden craters but also throughout what's known as the lunar regolith. The regolith is a fine layer of all the powder and bits of rock that has accumulated on top of the Moon's surface over the eons.
While the quick and obvious explanation for all this water near the Moon's surface is that it all comes from comet impacts — and indeed, that's likely part of any explanation — the main driver behind the Moon's water supply might be something else. There's a decades-old theory that suggests the Sun could send out streams of ionized hydrogen atoms — protons, in other words — which could combine with oxygen found on the Moon's surface to form water and water-related compounds known as hydroxyls, which are composed of one oxygen atom and one hydrogen atom.
This solar wind hypothesis is an intriguing idea, not least because it would mean that the process of water formation wouldn't be unique to the Moon — anywhere with a decent supply of oxygen atoms could generate water using this method. And the researchers' spectroscopy analyses of samples collected during the Apollo missions suggest the solar wind theory is a winner. The samples contain large amounts of hydroxyls. University of Michigan researcher Youxue Zhang explains in a statement:
We found that the 'water' component, the hydroxyl, in the lunar regolith is mostly from solar wind implantation of protons, which locally combined with oxygen to form hydroxyls that moved into the interior of glasses by impact melting. Lunar regolith is everywhere on the lunar surface, and glasses make up about half of lunar regolith. So our work shows that the 'water' component, the hydroxyl, is widespread in lunar materials, although not in the form of ice or liquid water that can easily be used in a future manned lunar base."
Fellow researcher Yang Liu says this also likely means there's water on the asteroids Vesta and Eros, as well as the innermost planet Mercury. For more, check out the original paper over at Nature Geoscience.
Image by puuikibeach on Flickr.