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Moon is rusting because of Earth’s oxygen: Study


BENGALURU: Almost 12 years after it was launched, Chandrayaan-1 has helped scientists find data revealing that parts of the Moon are rusting because of oxygen from Earth. The data was picked up by one of the 11 payloads on board Chandrayaan-1, an imaging spectrometer called Moon Mineralogy Mapper (M3) developed by the Brown University and Jet Propulsion Laboratory (JPL under US NASA funding), which was designed to map the surface mineral composition.

The payload which is among the six foreign payloads on board Chandrayaan-1 was activated on December 17, 2008. Researchers from the Hawai’i Institute of Geophysics and Planetology (HIGP) at the School of Ocean and Earth Science and Technology (SOEST), while analysing the M3 data, found oxidised iron mineral hematite in high latitudes of the Moon. The study, led by Shuai Li, assistant researcher at HIGP, was published on September 2 in Science Advances.

Li and another HIGP professor Paul Lucey, along with co-authors from NASA’s JPL, analysed the hyperspectral reflectance data acquired by M3 to find iron rust on the Moon, a finding that has surprised scientists because while iron reacts with oxygen and starts rusting, the lunar surface and its interior are devoid of oxygen.

The researchers observed that hydrogen in the solar winds on the lunar surface oppose oxidation. And yet, the presence of highly oxidised iron-bearing minerals, such as hematite, on the Moon led researchers to conclude that the rusting of iron on the moon can only be because of the Earth. “Our hypothesis is that lunar hematite is formed through the oxidation of iron on the lunar surface by oxygen from the Earth’s upper atmosphere that has been continuously blowing on the surface by solar winds when the Moon was in the Earth’s magnetotail during the past several billion years,” said Li.

“More hematite on the lunar nearside suggested that it may be related to Earth. This reminded me of a discovery by the Japanese Kaguya mission that solar winds  can blow oxygen from the Earth’s upper atmosphere to the lunar surface when the Moon is in the Earth’s magnetotail. Earth’s atmospheric oxygen could be a major oxidant to produce hematite.

Water and interplanetary dust may also have played critical roles.” After analysing the data, researchers felt that hematite oxidation at higher latitudes could also be because of water molecules in the lunar soil.  Interestingly, on November 14, 2008, it was India’s own payload - the Moon Impact Probe (MIP) — on board Chandrayaan-1 which made a controlled impact on the lunar south pole’s Shackleton Crater and raised a lunar dust plume to discover water molecules in the lunar soil.