(CNN) The moon is rusting.
The scientists had the same reaction that you probably had when they came to this conclusion. It shouldn’t be possible, after all, there is no oxygen on the moon, one of the two essential elements to create rust, the other being water.
But the evidence was there.
India’s lunar probe, Chandrayaan-1, orbited the moon in 2008 and collected data that has led to numerous discoveries over the years, including the revelation that there are water molecules on its surface. The probe also carried an instrument built by NASA that could analyze the mineral composition of the moon.
When researchers from NASA and the Hawaii Institute for Geophysics and Planetology analyzed the data recently, they were surprised to find hints of hematite, a form of iron oxide known as rust. There are many iron-rich rocks on the moon, but rust only occurs when iron is exposed to oxygen and water.
At first, I totally didn’t believe it. It should not exist under the conditions present on the Moon,” Abigail Fraeman, a scientist at NASA’s Jet Propulsion Laboratory, said in a news release.
Not only is there no air on the moon, but it is awash in hydrogen flowing in from the sun, carried by the solar wind. Rust occurs when oxygen removes electrons from iron; hydrogen does the opposite by adding electrons, which means it’s even harder for rust to form on the hydrogen-rich moon.
“It’s very puzzling,” said Shuai Li of the University of Hawaii, lead author of the study, which was published Wednesday in the journal Science Advances. “The Moon is a terrible environment for hematite to form.”
After months of research, Li and NASA scientists believe they have cracked it, and the answer to the mystery lies on our own planet.
here is his theory
One important clue was that the rust was more concentrated on the Earth-facing side of the moon, suggesting that it was somehow linked to our planet.
Earth is surrounded by a magnetic field, and the solar wind stretches this bubble to create a long magnetic tail downwind. The moon enters this tail three days before it is full, and it takes six days to cross the tail and out the other side.
During these six days, Earth’s magnetic tail coats the moon’s surface with electrons, and all kinds of strange things can happen. Dust particles on the moon’s surface could float to the ground and lunar dust could become a dust storm, according to NASA.
And, Li speculated, oxygen from Earth travels in this magnetic tail to land on the moon, where it interacts with lunar water molecules to create rust.
The magnetic tail also blocks almost all of the solar wind during a full moon, meaning the moon is temporarily shielded from the hydrogen explosion, opening a window for rust to form.
“Our hypothesis is that lunar hematite is formed through the oxidation of lunar surface iron by oxygen from Earth’s upper atmosphere that has been continuously blown to the lunar surface by the solar wind when the Moon is in the Earth’s magnetic tail for the past few billion years. Li said in a University of Hawaii news release.
“This discovery will reshape our knowledge of the Moon’s polar regions,” he added. “Earth may have played an important role in the evolution of the Moon’s surface.”
This theory could also explain why rust has been found on other airless bodies such as asteroids. “It could be that small bits of water and the impact of dust particles are allowing the iron in these bodies to oxidize,” Fraeman said.
But some questions remain unanswered, for example, while most of the rust was found on the near side of the moon, some smaller traces were also detected on the far side, where oxygen from Earth shouldn’t be able to reach. It’s also unclear how exactly the water on the moon interacts with the rock.
To collect more data on these unsolved mysteries, NASA is building a new version of the instrument that collected all of this existing data on the moon’s mineral composition. One of these features will be able to map water ice in craters on the moon, and “could also reveal new details about hematite,” the NASA statement said.