Finding rust on the Moon seems utterly illogical. After all, our celestial neighbor lacks both liquid water and a breathable atmosphere, and it’s constantly bombarded by solar particles. Yet, scientists have now confirmed that iron-rich lunar soil is indeed oxidizing into hematite, a common form of rust. This astonishing chemical process is being driven by oxygen ions escaping Earth’s upper atmosphere, as revealed by new laboratory experiments and satellite observations. This ground-breaking discovery suggests the Moon is far more chemically active than we ever imagined.
Earth’s Influence: The “Earth Wind” and Lunar Oxidation
In a study published in Geophysical Research Letters, researchers simulated lunar conditions by bombarding iron-rich powders with high-energy oxygen and hydrogen ions. They found that oxygen ions—similar to those streaming from Earth’s magnetotail, a phenomenon dubbed ‘Earth wind’—could easily transform iron and ilmenite into hematite, even without liquid water. While hydrogen from the solar wind typically inhibits this process, its energy levels were too low to prevent rust formation. This creates a delicate balance where oxidation can occur.
Why Does Lunar Rust Persist, Especially on the Near Side?
This lunar rust, or hematite, is particularly prevalent near the Moon’s poles and on the side that always faces Earth. This pattern makes sense: each month, as the Moon swings through Earth’s magnetotail, our planet’s oxygen ions are deposited onto the lunar surface. Crucially, this passage also shields the Moon from most of the hydrogen in the solar wind, which would otherwise counteract the oxidation process. This periodic protection allows rust to form and persist. Data from India’s Chandrayaan-1 orbiter and NASA’s Lunar Reconnaissance Orbiter align perfectly with these lab results, showing distinct hematite patches where Earth’s atmospheric influence meets minimal hydrogen.