Rocks collected by the Chinese Yutu moon rover in 2013 are unlike any other kind of regolith ever found on the lunar surface, suggesting that the history of the moon could be more complex than previous believed, according to a new Nature Communications study.
Zongcheng Ling of Shandong University in Weihai, China and his colleagues conducted an in-depth analysis of rocks collected by Yutu from its landing spot—a crater now known as Zi Wei located in the Mare Imbrium region of the moon. It marked the first study of geological samples from the moon in roughly four decades, according to Gizmodo.
Mare Imbrium originally formed about three billion years ago when an extremely large object hit the moon, causing lava to flood the surface and eventually cool. The more recently formed Zi Wei crater exposed some of the basalt rock that formed when that lava cooled, which is what was collected by the Yutu rover and analyzed by Ling’s team in the new study.
They found that the basalt had completely different concentrations of several minerals, including iron oxide, calcium oxide, and titanium dioxide, than were found in samples collected during the Apollo program and the Russian Luna probes during the 1970s, said New Scientist. The findings suggest that the moon is more geologically diverse than previously believed.
Impactors may have disrupted the moon’s mantle formation
Once Yutu collected samples of the lunar regolith, it analyzed those rocks using its alpha-particle X-ray spectrometer and near-infrared hyper spectral imager, and found what Gizmodo said were “intermediate concentrations” of titanium oxide in the form of a mineral called ilmenite. Ilmenite is one of the first minerals to cool out of magma due to its low melting point, they noted.
The mineral sinks into the mantle as it crystallizes, forming pockets that are rich in titanium. The compositions of the Apollo and Luna samples were either high or low in titanium based on levels of ilmenit found in various regions. The intermediate levels found in the new sample suggest that impacts during the moon’s magma ocean stage may have disrupted mantle formation.
“We’re still trying to figure out exactly how this happened,” study co-author Bradley Jolliff said in a statement, according to Gizmodo “The diversity tells us that the Moon’s upper mantle is much less uniform in composition than Earth’s,” he added, “and correlating chemistry with age, we can see how the Moon’s volcanism changed over time.”
The analysis also helped solve a mystery originally discovered by the Chang’e-3 lander while it was in orbit. The spacecraft detected both ilmenite and olivine, a mineral that crystallizes out of magma far earlier than ilmenite, in the same region of the landing site. The oddity was explained, however, by the discovery that the olivine is iron-rich, which lowers its melting temperature.
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Feature Image: Chinese Lunar Exploration Program/ China National Space Administration
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