The Moon is rusting, and Earth is to blame

At first glance, it seems impossible: the Moon has neither oxygen nor water in the amounts we know on Earth, both usually essential for rust to form. Yet recent research shows the oxygen driving this process actually comes from Earth itself.

Most of the time, both Earth and the Moon are exposed to the solar wind, a stream of charged particles from the Sun. But for about five days each month, Earth shields the Moon from that flow. During this period, the Moon is instead immersed in what scientists call the “Earth wind”, a stream of particles from Earth’s atmosphere, pushed into space and carried to the Moon by our planet’s magnetic field.

The Earth wind contains ions of oxygen, hydrogen, and nitrogen. When they strike the lunar surface, they embed themselves in the upper layers of soil and spark chemical reactions. Oxygen in particular can react with iron and other minerals, turning them into hematite, the very substance we know as rust.

To test the idea, an international team of scientists carried out a series of laboratory experiments. They recreated the conditions of the Earth wind by accelerating oxygen and hydrogen ions and directing them at mineral samples similar to those found on the Moon - iron, ilmenite, troilite, and magnetite.

The formation and preservation of hematite on the Moon depend on competing processes: oxygen ions from Earth wind oxidize iron-bearing minerals to hematite, while high-energy hydrogen ions can reduce hematite back to metallic iron. The balance between these ions determines how much hematite remains on the lunar surface.

The largest concentrations of hematite have been found near the Moon’s poles. Scientists link this to the way charged particles move. Heavier oxygen ions are less affected by Earth’s magnetic field and tend to settle in the high-latitude regions of the Moon. Lighter, more mobile hydrogen ions are pushed aside, leaving oxygen free to act more effectively.

Researchers note that to fully confirm this theory, samples of lunar hematite need to be brought back to Earth so the oxygen can be directly analyzed. Upcoming missions may help with this task, including India’s Chandrayaan-3 and China’s Chang’e-7, both operating in the Moon’s polar regions.

Earlier, Kazinform News Agency reported that Chinese researchers identified new landslides on the Moon.