Earth’s Oxygen Explains Mysterious Rust Formation on the Moon

Rust on the Moon does not make any sense: there is neither liquid water nor air to breathe, nor a constant torment by the solar particles. But now scientists can verify that iron-bearing lunar soils are able to oxidize into hematite, the mineral oxidation of rust. The factor contributing to the surprising chemistry is the evidence of new laboratory experiments and satellite observations that oxygen ions escaping the upper atmosphere of the Earth could be driving this chemistry, which indicates that the Moon is not as inert as previously thought.

Earth, Wind, and Lunar Oxidation

According to research in Geophysical Research Letters, scientists recreated the lunar condition by firing powerful oxygen and hydrogen ions on iron-heavy powders. Oxygen ions, like the ones flowing in the magnetotail of the Earth, which is referred to as the Earth wind, effortlessly transformed iron and ilmenite into hematite in the absence of liquid water. The hydrogen found in the solar wind was too low in energy to reverse the process, and high-energy hydrogen is able to decrease hematite to metal, forming a fragile equilibrium.

Why Hematite Survives on the Near Side

Hematite is concentrated towards the poles of the Moon and on the Earth-facing side. When the Moon passes through the magnetotail of the Earth every month, oxygen is released to the surface, and most of the hydrogen that would otherwise cause iron reduction is prevented. This is a periodic shielding to enable oxidation to prevail. The Chandrayaan-1 orbiter of India and the Lunar Reconnaissance Orbiter of NASA have made observations that are consistent with the laboratory findings in showing patches of hematite where Earth winds interact with scant hydrogen flux.