Researchers have discovered that the moon is slowly rusting, and Earth is partly to blame for this. A new study, which studies data from the Indian Space Research Organization's Chandrayaan-1, reveals that its poles have a very different composition than the rest of the moon.
By studying light reflected from the poles, Shuai Li of the University of Hawaii found the spectral signature of hematite. Hematite is a form of iron oxide, commonly known as rust. However, for iron to become rust, oxygen must be present, which the moon is known to lack.
"It's very puzzling," Li said in a statement. "The moon is a terrible environment for hematite to form."
"At first, I didn't really believe it. It shouldn't exist based on the conditions on the moon," said Abigail Fraeman, one of the JPL. "But ever since we discovered water on the moon, people have speculated that there could be a greater variety of minerals than we thought, if the water had reacted with rocks."
The presence of rust can be explained in three ways. Although the moon has no atmosphere, it has traces of oxygen due to Earth's magnetic field. Oxygen can travel through Earth's magnetic field. This would explain why there is a larger quantity of hematite on the side of the moon that faces Earth.
It is also possible that more oxygen was transferred to the moon when it was closer to Earth, as the two bodies have drifted apart from each other for billions of years.
Another cause is the amount of hydrogen present on the moon. Hydrogen bombards both the moon and Earth, traveling through space via solar winds from the Sun.It is also a solvent, meaning it adds electrons to the materials it comes into contact with, as opposed to an oxidizer, which removes electrons.
The Earth's magnetic field protects it from this, but the moon has no such protection.
However, Earth's magnetic field, as well as the transport of oxygen to the moon, also blocks almost all solar wind activity whenever it's full. This means there's an opportunity for rust to form during the moon's lunar cycle.
The third factor is the water ice that exists on the Moon, located beneath lunar craters at the edge of the Moon. Li reported that dust particles that regularly strike it could release these water molecules, mixing with iron, and then heated to increase the oxidation rate.
This would explain why hematite was found far from the moon's craters, however, further research is required to fully explain how water interacts with rock. Such research could explain why hematite was found on other bodies, such as asteroids.
"It could be that small water droplets and the impact of dust particles allow the iron in these bodies to rust," Fraeman said.
