Tag Archives: hematite

The mystery of rust on the Moon

Link here. The data shows that there is rust on the Moon, in an environment lacking oxygen and water that should make it impossible for it to form.

Yet the rust is there, in the form of hematite, and in fact the data from India’s first lunar orbiter, Chandrayaan-1, has found that the Moon’s nearside has much more of it. To explain how it got there the scientists have come up with a complex hypothesis, first requiring the Moon to be shielded from the Sun’s solar wind by the Earth’s magnetic field for part of its orbit, then having that magnet field transport oxygen from the Earth’s upper atmosphere to the Moon.

This oxygen then reacts with the tiny amount of water that some scientists believe Chandrayaan-1 detected scattered in the Moon’s regolith, the equivalent of its topsoil. The result, according to this hypothesis, is that over time that oxygen and water reacted with the surface iron on the Moon’s nearside, facing the Earth, causing it to rust.

The explanation is elegant, and fits the known facts (though the presence of that water in the lunar regolith remains unconfirmed). It is also complex, which should raise doubts. Regardless, the nearside of the Moon appears to have more hematite than the farside, and the formation of that iron oxide remains baffling.