The Moon Is Rusting, and Researchers Want to Know Why
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The Moon Is Rusting, and Researchers Want to Know Why:
A new paper in Science Advances reviews data from the Indian Space Research Organization's Chandrayaan-1 orbiter, which discovered water ice and mapped out a variety of minerals while surveying the Moon's surface in 2008. Lead author Shuai Li of the University of Hawaii has studied that water extensively in data from Chandrayaan-1's Moon Mineralogy Mapper instrument, or M3, which was built by NASA's Jet Propulsion Laboratory in Southern California. Water interacts with rock to produce a diversity of minerals, and M3 detected spectra - or light reflected off surfaces - that revealed the Moon's poles had a very different composition than the rest of it.
Intrigued, Li homed in on these polar spectra. While the Moon's surface is littered with iron-rich rocks, he nevertheless was surprised to find a close match with the spectral signature of hematite[*]. The mineral is a form of iron oxide, or rust, produced when iron is exposed to oxygen and water. But the Moon isn't supposed to have oxygen or liquid water, so how can it be rusting?
The mystery starts with the solar wind, a stream of charged particles that flows out from the Sun, bombarding Earth and the Moon with hydrogen. Hydrogen makes it harder for hematite to form. It's what is known as a reducer, meaning it adds electrons to the materials it interacts with. That's the opposite of what is needed to make hematite: For iron to rust, it requires an oxidizer, which removes electrons. And while the Earth has a magnetic field shielding it from this hydrogen, the Moon does not.
"It's very puzzling," Li said. "The Moon is a terrible environment for hematite to form in." So he turned to JPL scientists Abigail Fraeman and Vivian Sun to help poke at M3's data and confirm his discovery of hematite.
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