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For about half of Earth’s 4.6 billion years of existence, the atmosphere contained only carbon dioxide and nitrogen, with no oxygen. But this changed when cyanobacteria, also known as blue-green algae, began to produce the first oxygen using nitrogenase, leading to the Great Oxidation Event, which fueled the evolution of life on Earth.
Rust discovered in the high latitudes of the Moon
To the surprise of many planetary scientists, oxidized reddish-brown iron ore hematite has been discovered at high latitudes on the Moon, changing our understanding of the Moon’s polar regions. “The Earth may have played an important role in the evolution of the Moon’s surface,” says Shuai Li, an assistant researcher at the Hawai’i Institute of Geophysics and Planetology (HIGP) at the University of Earth’s School of Ocean and Earth. H Hawai’i Mānoa. Science and Technology (SOEST).
Thought it’s a scientific impossibility
Scientists led by Li now speculate in the journal Science Advances that the Earth’s life-giving oxygen, highly reactive with iron, was carried to the Moon’s poles by the wind, creating what was thought to be a scientific impossibility. , rust, a reddish brown rust left behind. when iron atoms react with oxygen and water in what is known as an oxidizing or electron-wasting reaction, where solar winds constantly hit its cratered surface with charged hydrogen, causing it to have a highly reducing or reducing condition. electron gain that prohibits oxidation.
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However, the surface and interior of the Moon are virtually devoid of oxygen, so pristine metallic iron is prevalent on the Moon, and highly oxidized iron has not been confirmed in samples returned from the Apollo missions. Also, hydrogen from the solar wind hits the lunar surface, which acts in opposition to oxidation. So the presence of highly oxidized iron-containing minerals, such as hematite, on the Moon is an unexpected discovery.
When the moon is on the Earth’s magnetic tail
“Our hypothesis is that lunar hematite is formed through the oxidation of iron on the lunar surface by oxygen in the Earth’s upper atmosphere that has been continuously drawn to the lunar surface by the solar wind when the Moon is in the Earth’s magnetic tail for the past billions of years. ” Said Li, whose research was inspired by his earlier discovery of water in the Moon’s polar regions in 2018.
“I don’t think anyone expected this on the surface of the Moon,” said Li, the first author of the paper. “This is the basic chemistry; we all know that the lunar surface is shrinking a lot, so there is no reason why you can see a high-valence iron like hematite.”
To make this discovery, Li, HIGP professor Paul Lucey, and co-authors from NASA’s Jet Propulsion Laboratory (JPL) and elsewhere analyzed hyperspectral reflectance data acquired by the Moon Mineralogy Mapper (M3) designed by the NASA’s JPL aboard India’s Chandrayaan-1 mission.
“When I examined the M3 data in the polar regions, I found that some spectral features and patterns are different from what we see at lower latitudes or the Apollo samples,” Li said. “I was curious to know if it is possible that there are water-rock reactions on the Moon. After months of research, I discovered that I was seeing the hematite signature. “
Concentrated on the near side of the moon
The team found that the locations where there is hematite are strongly correlated with the water content at the high Li latitude and others previously found and are more concentrated on the near side, which always faces Earth.
“More hematite on the lunar near side suggested it could be related to Earth,” Li said. “This reminded me of a discovery by the Japanese Kaguya mission that oxygen from Earth’s upper atmosphere can be carried to the lunar surface by the solar wind when the Moon is on Earth’s magnetic tail. So atmospheric oxygen on Earth could be the main oxidant to produce hematite. Water and the impact of interplanetary dust may also have played a key role “
“Interestingly, hematite is not absolutely absent from the far side of the Moon, where oxygen from Earth could never have reached, although far fewer exposures were observed,” Li said. “The small amount of water (<~ 0.1% by weight) observed at high lunar latitudes may have been substantially involved in the hematite formation process on the lunar opposite side, which has important implications for interpreting the hematite observed in some S poor in water -type asteroids ".
The research team hopes that NASA ARTEMIS missions will be able to return samples of hematite from the polar regions. The chemical signatures of those samples can confirm your hypothesis whether lunar hematite is oxidized by Earth’s oxygen and can help reveal the evolution of Earth’s atmosphere over the past billions of years.
The Daily Galaxy, Jake Burba, via UH Mānoa School of Ocean and Earth Science and Technology (SOEST)
Image Credit: NASA
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