A facelift for the Moon every 81,000 years

The Moon is bombarded by so much space rock that its surface gets a complete facelift every 81,000 years, according to a study released Wednesday based on NASA data.

This churn — affecting the top two centimetres (nearly an inch) of mostly loose moon dust — happens 100 times more frequently than previously thought, scientists reported.

The moon is shown from this photo taken in Cordoba, Argentina, on Oct 11. (AFP)

The study also estimates that asteroids and comets crashing into Earth’s only natural satellite create, on average, 180 new craters at least 10 metres (33 feet) in diameter every year. The findings, published in Nature, come from “before and after” pictures taken by NASA’s Lunar Reconnaissance Orbiter spacecraft, which has been mapping the Moon since 2009.

By comparing images of the same area at regular intervals, a team of scientists led by Emerson Speyerer from Arizona State University in Tempe were able to tally the number of new craters and extrapolate to the entire surface of the Moon.

“We detected 222 new impact craters and found 33 percent more craters with a diameter of at least 10 metres than predicted” by earlier models, the researchers concluded.

The scientists also found thousands of subtler disturbances on the surface, which they described as “scars” from smaller, secondary impacts that — over thousands of years — churned up the top layer of the Moon without creating craters. (AFP)