The moon is getting a makeover: 180 new craters appear on the lunar surface every year

By AFP and ABIGAIL BEALL FOR MAILONLINE for the Daily Mail.

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

The study also estimates that asteroids and comets crashing into Earth’s only natural satellite create, on average, 180 new craters at least 33 feet (10 metres) in diameter every year.

This is a third more than previous estimates, and it means astronauts visiting the moon will have to be more careful to avoid the flying space rocks.

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 (shown above)

METEORITES ON EARTH

Earth is also constantly pelted by asteroids and meteors, but is protected by a thick atmosphere.

More than 100 tonnes of dust and sand-sized particles rain down on the planet every day.

Even space rocks up to across 80 feet (25 metres) will likely explode and disintegrate in the upper layers of our atmosphere, causing little or no damage, according to Nasa.

The Moon’s ultra-thin atmosphere only contains about 100 molecules of gases and elements per cubic centimetre (0.6 cubic inch).

Earth’s atmosphere at sea level, by contrast, is packed with about 100 billion billion molecules per cubic centimetre.

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

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

Small meteors regularly impact the moon and Earth, where they usually burn up in the atmosphere or land in uninhabited areas and are not detected.

But on the moon, these impacts constantly form craters and basins.

‘It’s just something that’s happening all the time,’ said Emerson Speyerer, lead author of the paper.

The scientists also found thousands of subtler disturbances on the surface, which they described as ‘scars’ from smaller, secondary impacts.

These smaller impacts, over thousands of years, churned up the top layer of the moon without creating craters.

This churn, affecting the top 0.6 inches (two centimetres) of mostly loose moon dust, happens 100 times more frequently than previously thought, scientists reported.

This means planetary geologists will also need to rethink their understanding of the age of the lunar surface.

Models of how old the moon’s surface is depend on counting craters and estimating how long the terrain has been pummelled to form the number of craters seen today.

If the craters form more quickly than we thought, it means the surface is likely to be younger than previous estimates.

A colourised topography of the moon’s surface. 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

This image shows a close-up of the newly-discovered 39 foot (12 metre) diameter impact crater, which formed between 25 October 2012 and 21 April 2013. Meteorites have created at least 222 impact craters into the moon’s surface in the past 7 years, the study found

Although most of the craters on the moon’s surface formed millions of years ago, meteorites continue to create fresh marks.

Along with the fresh craters, the team found more than 47,000 ‘splotches’ – these are formed when material gets kicked up by the main impact and rains down.

This means a bigger risk for any future lunar habitats, Stephanie Werner, a planetary geologist at the University of Oslo told Nature.

Example of a low reflectance (top) and high reflectance (bottom) splotch, created either by a small impacts or from material ejected and raining down from another impact. In both cases, the top few centimeters of the soil was churned up by the impact

Earth is also constantly pelted by asteroids and meteors, but is protected by a thick atmosphere.

More than 100 tonnes of dust and sand-sized particles rain down on the planet every day.

Even space rocks up to across 80 feet (25 metres) will likely explode and disintegrate in the upper layers of our atmosphere, causing little or no damage, according to Nasa.

The Moon’s ultra-thin atmosphere only contains about 100 molecules of gases and elements per cubic centimetre (0.6 cubic inch).

Earth’s atmosphere at sea level, by contrast, is packed with about 100 billion billion molecules per cubic centimetre.

The study estimates that asteroids and comets crashing into the moon create close to 180 new craters at least 32 feet (10 metres) in diameter every year. Earth is also pelted by asteroids and meteors, but is protected by a thick atmosphere