Meteorites pummel the Moon far more than expected

Hundreds of fresh impact craters hint at possible dangers for future lunar bases. Meteorites have punched at least 222 impact craters into the Moon’s   surface in the past 7 years. That’s 33% more than researchers expected,   and suggests that future lunar astronauts may need to hunker down   against incoming space rocks. “It’s just  something that’s happening all the time,” says Emerson  Speyerer, an  engineer at Arizona State University in Tempe and author  of a 12 October  paper in naturePlanetary  geologists will also need to rethink their understanding of the age of  the lunar surface, which depends on counting craters and estimating how  long the terrain has been pummelled by impacts.  Although most of the craters dotting the Moon’s surface formed  millions of years ago, space rocks and debris continue to create fresh  pockmarks. In 2011, a team led by Ingrid Daubar of NASA’s Jet Propulsion  Laboratory in Pasadena, California, compared some of the first pictures  taken by NASA´s Lunar Reconnaissance Orbiter (LRO), which launched in 2009, with decades-old images taken by the Apollo astronauts. The scientists spotted five fresh impact craters in the LRO images. Then, on two separate occasions in 2013, other  astronomers using telescopes on Earth spotted bright flashes on the  Moon; LRO later flew over those locations and photographed the freshly  formed craters. <h2>Forever young</h2> LRO  has taken about a million high-resolution images of the lunar surface,  but only a fraction cover the same portion of terrain under the same  lighting conditions at two different times. Speyerer’s team used a  computer program to automatically analyse 14,092 of these paired images,  looking for changes between the two. The 222 newfound craters are  distributed randomly across the lunar surface, and range between 2 and  43 metres in diameter.  There are more fresh  craters measuring at least 10 metres across than standard cratering  calculations would suggest. This could mean that some young lunar  surfaces may be even younger than thought, says Daubar. She calls the  work “a significant advance in the field of crater chronology”, noting  that it can even be used to compare cratering rates on the Moon and  Mars.  Meteorites can churn up the lunar  surface in several ways. Along with the fresh craters, Speyerer’s team  found more than 47,000 ‘splotches’, formed when material gets kicked up  by the main impact and rains down — sometimes tens of kilometres away.  And  that means a bigger risk for any future lunar habitats, says Stephanie  Werner, a planetary geologist at the University of Oslo. The chances of a  lunar base being nailed by a direct meteorite hit are relatively small,  but the splattered material could pose a hazard. Werner is part of a  team that has proposed a combined orbiter-lander misson to the European Space Agency, which would study impact flashes at the Moon and quantify the risk. Quelle: http://www.nature.com/news/meteorites-pummel-the-moon-far-more-than-expected-1.20777

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