Moon craters may harbour alien minerals, says study

According to a new study, Moon craters hold a treasure-trove of minerals that may have originated from a source 'not of that world'.

Looking up at the Moon's cratered surface, it's clear that it has seen a lot of impacts over the years. Scientists studying rocks brought back by the Apollo missions and data sent back by orbiting satellites have found that some craters contain 'unusual' minerals, such as olivine and magnesium-rich spinel. It was assumed that these were either deposited there by the meteorite that hit the surface, or were dug up from under the surface by the impact, however any impact powerful enough to do that would have also been powerful enough to almost completely destroy these minerals, leaving behind only traces. So, finding the larger deposits of these minerals couldn't be explained.

Now, a team of researchers at Purdue University in Indiana believe they may have the explanation.

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Developing a computer model that would account for the effects of slamming meteorites into the Moon, including the effect of those impacts on the minerals both in the meteorites and in the Moon's surface, the researchers found that slower impacts would allow larger deposits of these minerals to survive. According to the research paper, they concentrated their study on Copernicus, a nearly 100 km-wide crater that has shown evidence of having both olivine and spinel in its central peak, but they also looked at the Theophilus and Tycho craters, due to the 'exotic' magnesium-rich spinel detected there.

"These computations show that, whereas most of the ... projectile is vaporized and little remains in the crater at impact velocities above 14 kilometres per second, much of it survives the impact at velocities less than 12 kilometres per second," they wrote in the research paper.

"We conclude that some unusual minerals observed in the central peaks of many lunar impact craters could be exogenic in origin and may not be indigenous to the Moon."

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In a review of the research study, Arizona State University planetary physicist Erik Asphaug, agrees with some of the study's findings, but also points out a few potential snags, and also adds some compelling insight.

"The model could explain the presence of spinel deposits in craters large enough to form central peaks," he wrote. "However, lunar spinels ... also occur in patches on crater floors and rims, and, more difficult to explain, in basaltic plains located far from craters."

"As for Copernicus specifically," he added, "the large volumes of melted rock throughout the crater indicate a high-velocity impact, not a slow one."

However, he agrees that some of the minerals may have been left behind by low-velocity meteorite impacts, and he adds that some of it may be from low-velocity impacts of material ejected by large impacts on Earth.

"Even more provocative is the suggestion that we might someday find Earth’s protobiological materials, no longer available on our geologically active and repeatedly recycled planet, in dry storage up in the lunar 'attic'," he wrote. "Certainly, the potential of finding early Earth material is emerging as one of the primary motivations for a return to the Moon by human astronauts in our ongoing search for the origin of life."

(Images courtesy: NASA)

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