The Moon is rusting, but we don't know exactly why

On the lunar surface there is hematite, an iron oxide. A real surprise for scientists, who until now considered the conditions of water and oxygen prohibitive. So how is this possible?

(image: Getty Images) More than 50 years after Apollo 11, the Moon continues to conceal many mysteries. By analyzing data collected by the Moon Mineralogy Mapper (or M3) of the Indian orbiter Chandrayaan-1, scientists have just discovered that on the surface of our satellite there would be some rust, to be precise hematite. Too bad that it should not be possible in the absence of liquid water and oxygen, essential for the oxidation of the iron contained in the lunar rocks. The puzzling revelation, along with a possible explanation, is published in the pages of Science Advances.

Lunar rust

Hematite is an iron oxide (Fe 2 O 3), a molecule which is formed in an oxidation-reduction process that is a reaction in which an element loses electrons (oxidizes) in favor of a more reactive element (which is reduced).

For the reaction to take place, explains Shuai Li of the University of Hawaii and lead author of the research, along with iron there must be oxygen and liquid water. And on the Moon these conditions, apparently, do not exist: the data collected by the numerous instruments that we have sent to the satellite to investigate its nature indicate that in the craters of its hidden side there is ice, not liquid water; the Moon, then, does not have an atmosphere and oxygen is present only in trace amounts. Moreover, our satellite is for most of the time exposed to the action of the solar wind, which carries hydrogen: in practice, electrons come from the Sun which make it even more difficult for oxidation reactions to occur.