Our closest global neighbor, the moon, and the only other body in the solar system, on which man has set foot, is well known to us. We know that there is practically no air. We know that water is ice, but not liquid water.
So you can understand why the investigation of hematite on the moon confuses scientists, as hematite is an oxidized form of iron that needs the presence of both air and water here on Earth.
Especially on the moon there is a constant bombardment with the flow of hydrogen from the solar wind, a decreasing agent that ‘donates’ its material to the material that comes in contact with it. Oxidation is caused by the loss of electrons – so even if all the right elements for oxidation were present, the solar wind should cancel it out.
“It’s amazing,” said Shuai Lee, a planetary scientist at the University of Hawaii at Manoa. “The moon is a terrible environment for making hematite.”
An elevated map of hematite at the Moon’s North Pole. (Shuai Li)
The data collected by the Chandrayaan-1 orbiter of the Indian Space Research Organization has discovered a question mark in hematite. Moon Mineral Gy Gi Mapper (M3), designed by NASA’s Jet Propulsion Laboratory, uses hyperspectral imaging to perform granular spectroscopic analysis, which gives a detailed breakdown of the lunar surface mineral composition.
In this way, Lee and his colleagues identified the accumulation of ice at lat latitudes around the lunar poles in 2018. But, while he was checking the data, Lee saw something strange.
“When I examined the M3 data in the polar regions, I found that some spectral features and patterns are different than what we see on lower latitudes or Apollo samples,” Lee said.
“I was curious as to whether this is possible that there are water reactions on the moon. After months of investigation I found out that I was seeing the signature of hematite.”
Which raised a big question: How did Heck get there? Well, there may be a big indication of how hematite is delivered. It corresponds very strongly to the water markings previously identified and associated with the effect. Scientists believe that water ice can be mixed with lunar regolith, and excavated and melted during impact events.
Hematite is also most often found on the side of the moon which always faces the earth. That, according to the researchers, is really interesting.
“More hematite on the lunar nurseside suggests it may be related to Earth,” Lee said.
“I was reminded of the discovery by the Japanese Kaguya Mission that oxygen is blown to the lunar surface from the Earth’s atmosphere when the Moon is in Earth’s magnetism. Therefore, Earth’s atmospheric oxygen may be the main oxidant to produce hematite.”
During a full moon, our satellite is in Earth’s magnetotel, the rear area of the magnetosphere away from the sun. At this point, more than 99 percent of the solar wind hinders reaching the moon, meaning that the pesky hydrogen-reducing agent is not completing all of the oxidation process.
Combine these three components – a small amount of nuclear water, a small amount of oxygen, and a short window of time each month in which rust forms freely – and, in a few billion years, you can get hematite on the moon.
However, this does not mean that the mystery is completely solved.
“Interestingly, hematite is not completely absent from the far side of the moon where the Earth’s oxygen never reached, although very few exposures were observed,” Lee said.
“The small amount of water seen at lunar latitudes can be significantly involved in the formation of hematite on the far side of the moon, with important suggestions in interpreting hematite observed on some water-weak S-type asteroids.”
It would be really interesting to get your hands on the mineral. It is possible that deposits of hematite in a series of epochs could preserve oxygen isotopes of different ages throughout Earth’s history over billions of years. This can be really useful for understanding the atmospheric evolution of our planet.
And, of course, it would also be deeply enlightening to understand the history of the moon.
“This discovery will reshape our knowledge of the Moon’s polar regions,” Lee said. “Earth must have played an important role in the evolution of the lunar surface.”
Research has been published in Science progress.
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