In this false color image of the moon, the blue colors indicate the presence of water.
New research shows that the moon has rust on its surface, which is quite strange. When iron reacts with oxygen, rust forms and iron oxide forms. While rust is common on Earth, and even the surface of Mars, its presence on the Moon is unexpected.
The moon is mostly a dry, airless rock, but it has traces of water ice near its poles. This was discovered by the Chandrayaan-1 orbiter team of the Indian Space Research Organization in the year 2008. The team also located various minerals on the lunar surface, but was surprised to find hematite. Hematite is a form of iron oxide that normally forms when iron is exposed to oxygen and liquid water. While other processes can produce hematite, it is inhibited by the presence of hydrogen. Hydrogen is present on the surface of the moon due to solar wind. So how does hematite form on the moon?
A piece of hematite from northern Minnesota.
The team has a few ideas. One is that the moon can be shielded from the solar wind when it passes through the tail of the earth’s magnetic field. This can happen when the earth is between the sun and the moon. Another possibility is that micromittors regularly strike the moon. Their effects can free up water molecules on the lunar surface while allowing oxidation to occur while heating the surface.
It’s an exciting mystery, and one more question we’ll try to answer when we return to the moon as part of NASA’s Artemis program.
Reference: Shuai Li, et al. “Extensive hematite at high latitudes of the moon.” Science progress Volume 6, no. 36, (2020).
