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- Unexpected discovery: Despite lacking air and water, scientists detected hematite – a form of rust – on the Moon in 2020 via data from India’s Chandrayaan-1 mission
- Rust needs iron, oxygen, and water: While Moon rocks are rich in iron, the necessary oxygen and water shouldn’t be available, making this discovery puzzling
- Earth’s magnetic tail: Earth’s magnetic field stretches into space and forms a 'tail' that the Moon passes through for about six days each lunar cycle, near full Moon
- Borrowed oxygen: During those periods, Earth’s oxygen may hitch a ride along the magnetotail to the Moon, supplying the oxygen required for rust formation
- Solar wind protection: Earth's magnetotail also blocks most of the solar wind’s hydrogen (a reducer that prevents rust) during full Moon, creating a rare window for oxidation
- Moon’s water: Though there's no liquid water, water molecules and hydroxyl detected on the lunar surface (especially at the poles) could offer the moisture needed for rust to form
- Dust plays a role: Micrometeorite impacts may release or bring water molecules into contact with iron, helping trigger the rusting reaction when conditions align
- Mystery remains: This model explains why rust appears mainly on the near side facing Earth, but minor rust on the far side remains unexplained, and needs more data
Get the full story and all the facts in our news coverage explaining why the Moon is rusting
