Fresh craters point to constant 'churning' of moon's surface


More than 200 new craters popped up on the moon over the past seven years – a third more than expected. 



The moon's surface is completely turned over in around 80,000 years – not millions of years as once thought.

Comparing 14,000 pairs of 'before and after' photos snapped over seven years by the Lunar Reconnaissance Orbiter, a team from Arizona State University and Cornell University in the US found 222 new impact craters with diameter more than 10 metres – some 33% more than predictions – along with jets of freshly uncovered material.

Not only does this relatively rapid turnover, published in Nature, mean some of the moon's surface features are much younger than we suspect, but any structures we might one day build on the moon will need extra protection.

New impact craters, yellow dots, discovered by analysing 14,000 'before and after' images. The two red dots mark the location of the 17 March 2013 and the 11 September 2013 impacts that were recorded by Earth-based video monitoring.
NASA / GSFC / Arizona State University

Arizona State University's Emerson Speyerer, co-author of the study, said the high turnover rate comes not from extra micrometeorites peppering the lunar surface but from secondary impacts produced when debris kicked up by the initial collisions rains down again.

This new 12-metre impact crater formed between 25 October 2012 and 21 April 2013.
NASA / GSFC / Arizona State University

These can produce starburst-like patterns (see right for an example).

This secondary cratering process churns the top two centimetres of moon material more than 100 times faster than expected.

“In addition to the new impact craters and starburst debris patterns, we observed a surprising number of small surface changes which we call splotches,” Speyerer says.

Splotches don't have the distinct ring of a crater, so Speyerer and his crew think they're likely caused by small amounts of material thrown from larger impacts.

NASA recently approved a two-year mission extension for the Lunar Reconnaissance Orbiter. Perhaps, during that time, the probe will spot a big impact.

You can watch how the craters were imaged and detected in the video above.

In the video above, you can see how the craters were detected.

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  1. http://nature.com/articles/doi:10.1038/nature19829
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