Scientists Found Rust on the Moon

Rust requires oxygen, water, and the right conditions, all of which the Moon lacks. So where did a newly discovered iron oxide come from? Earth is one possibility. From a report: Contrary to what was thought to be a scientific impossibility, scientists detected rust -- a product that requires oxygen, water, and oxidative conditions -- on the surface of the Moon, a famously oxygen-poor, liquid water-less, and reducing environment that prohibits oxidation. The scientists speculated that the oxygen needed for the reaction that forms rust had been carried to the poles of the Moon by wind from the Earth, and a paper detailing the discovery was published on Wednesday in the journal Science Advances. Rust is the reddish-brown material left behind when iron atoms react with oxygen and water in what is known as an oxidizing, or electron-losing, reaction. The Moon's very thin atmosphere does not trap much oxygen, and solar winds constantly blast the surface of the Moon with charged hydrogen, causing it to have highly reducing, or electron-gaining, conditions.

So while rust is common on Earth, its discovery on the Moon caught researchers by surprise. "I don't think anyone expected this on the Moon's surface," said Shaui Li, the first author of the paper and a researcher at the University of Hawai'i at Manoa. "This is basic chemistry -- we all know that the lunar surface is highly reducing, so there is no reason you would be able to see a high-valence iron like hematite." By comparing reflectance data collected by the Indian Chandrayaan-1 mission to pure samples of rust, Li's group identified material at latitudes above 60 degrees on the Moon's surface as hematite, or iron (III) oxide. Li said that the comparison was fairly straightforward, and he is very confident that the reflectance spectra were of hematite.

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