Chandrayaan-1 data helps Nasa find moon may be rusting along poles: But is oxygen for rusting coming from Earth? | India News

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NEW DELHI: National Aeronautics and Space Administration (Nasa) scientists while analysing data and lunar images from India’s Chandrayaan-1 mission have found that Earth’s natural satellite may be rusting along the poles. But what intrigued the scientists the most is that in an airless moon, what is the source of oxygen for rusting to happen?
A new paper in “Science Advances” reviews data from Chandrayaan-1 orbiter, which had first discovered the concrete evidence of water ice on the moon and also mapped a variety of minerals on the lunar surface. Indian Space Research Organisation (Isro) had launched the moon mission in 2008, which also carried a Nasa payload Moon Mineralogy Mapper instrument or M3. While reviewing the Chandrayaan-1 data, US scientists were surprised to find evidence that the airless moon has rust on it as well. Lead author of the paper, Shuai Li, of the University of Hawaii extensively studied the data from M3.
Water interacts with a rock to produce a diversity of minerals and M3 detected spectra (light reflected off surfaces) that revealed the moon’s poles had a very different composition than the rest of it. Li focused on these polar spectra. While the moon’s surface is littered with iron-rich rocks, he was surprised to find a close match with the spectral signature of hematite. The mineral is a form of iron oxide or rust, produced when the iron is exposed to oxygen and water. But the moon isn’t supposed to have oxygen or liquid water, so how can it be rusting? Li turned to Nasa’s Jet Propulsion Laboratory scientists Abigail Fraeman and Vivian Sun to help study M3’s data and confirm his discovery of hematite.
After their own study, Fraeman and Sun were convinced that M3’s data indicated the presence of hematite at the lunar poles. “In the end, the spectra were convincingly hematite-bearing, and there needed to be an explanation for why it’s on the moon,” Sun said. Their paper offers a three-pronged model to explain how rust might form in such an environment.
The source of that oxygen could be our planet. Earth’s magnetic field trails behind the planet like a windsock. In 2007, Japan’s Kaguya orbiter discovered that oxygen from earth’s upper atmosphere can hitch a ride on this trailing magnetotail, travelling 385,000 km to the moon. That discovery fits with data from M3, which found more hematite on the moon’s earth-facing near side than on its far side. “This suggested that earth’s oxygen could be driving the formation of hematite,” Li said.
The moon has been inching away from the earth for billions of years, so it’s also possible that more oxygen hopped across this rift when the two were closer in the past. Then there’s the matter of all that hydrogen being delivered by the solar wind. But more data is needed to determine exactly how the water is interacting with the rock. That data could help explain another mystery: why smaller quantities of hematite are also forming on the far side of the Moon, where the earth’s oxygen shouldn’t be able to reach it.
With India planning to launch the Chandrayaan-3 mission early next year and Nasa also gearing up to send dozens of instruments to Moon in 2021 and preparing to send astronauts again to the moon under its Artemis programme by 2024, the lunar science will again come to the fore, 50 years after the first Apollo landing.



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