Scientists have found that oxygen particles blown from Earth to the Moon can turn lunar minerals into haematite, also known as rust. During that time, the Moon is exposed mainly to particles that had been part of Earth’s atmosphere before blowing into space — a phenomenon known as Earth wind. The authors of the 2020 paper proposed that it might have arrived in the Earth wind. The results show that the Moon undergoes many chemical and mineralogical changes as it passes through the Earth wind each month, Jin says. Perhaps most importantly, they show that oxygen in the Earth wind can form haematite on the Moon.