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Moon craters may hold ancient asteroid materials
 Date: 2013-06-13  Page Views:

The Moon's impact craters may contain remnants of asteroids that created them, a new study finds.

Previously, asteroids responsible for the formation of large lunar impact craters are often assumed to melt or vaporize during the impact, so that only geochemical traces or small fragment remain in the final crater.

Dr. YUE Zongyu, a researcher at the Institute of Remote Sensing and Digital Earth (RADI) under the Chinese Academy of Sciences (CAS), in collaboration with planetary scientist Prof. H. Jay Melosh and his colleagues from Purdue University, used computer model to simulate the formation of impact craters exampled by Copernicus crater and found that for vertical impact velocities below about 12 km/s, the projectile material may both survive the impact and be swept back into the central peak of the final crater as it collapses under the moon's gravity, although it would be fragmented and strongly deformed. Contributors to the research also include RADI’s planetary remote sensing team members Prof. DI Kaichang, HU Wenmin, and LIU Yilang.

The simulations may explain the occurrence of minerals called olivine in the central peaks of many large lunar craters such as the 93 km-wide Copernicus.

Spinels and olivines are abundant in many asteroids, meteorites and chondrules, so it's possible that these 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, this study concluded.

The findings of the new study, was recorded in a paper titled "Projectile remnants in central peaks of lunar impact craters", published online May 26 in the journal Nature Geoscience.

The findings have other ramifications that materials projected from the Earth following powerful impacts in the geological ages and which impacted on the lunar surface at comparatively low velocities may also have been preserved on it.

"This raises the possibility of finding early Earth material," Erick Ashpaug of Arizona State University wrote in an accompanying commentary in the same issue of Nature Geoscience.

"Even more provocative is the suggestion that we might someday find Earth’s proto-biological materials, no longer available on our geologically active and repeatedly recycled planet, in dry storage up in the lunar 'attic'," Asphaug added.

In a way, therefore, the findings point out an intriguing prospect for further studying the composition of the lunar surface as well as other asteroids including the early Earth.

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