Meteorites hit Mars much more frequently than previously thought, a probe finds

Seismic recordings from a NASA space probe show that Mars is bombarded by basketball-sized meteorites almost daily, five times more often than previously thought.

Before the new study was published on Friday, the exact number of meteorite impacts on Mars could be estimated using images from orbiting spacecraft or models based on lunar craters.

But NASA’s InSight probe, which landed on a Martian plain called Elysium Planitia in 2018, allowed scientists to hear the red planet’s inner rumblings for the first time.

Mars is about twice the size of the Moon and lies much closer to our solar system’s main asteroid belt, making it a prime target for large chunks hurtling through space.

Most meteorites that hit Earth break up in our atmosphere. However, Mars’ atmosphere is 100 times thinner than Earth’s and therefore offers little protection.

Instead of having to sift through images taken from afar, the international team of researchers behind the new study in Nature Astronomy were able to listen in on meteorites hitting Mars.

“If we want to understand how frequently impacts occur, listening for them seems more effective than looking for them,” said Gareth Collins, co-author of the study from Imperial College London, in a statement.

Using data from InSight’s seismometer, researchers estimated that Mars is hit by 280 to 360 meteorites each year, all leaving craters over eight meters in diameter.

“This rate was about five times higher than the number estimated based on orbital images alone,” said Geraldine Zenhaeusern of ETH Zurich, co-author of the study.

– Mars missions, watch out –

Due to frequent, violent dust storms, it is particularly difficult for spacecraft in Mars’ orbit to detect small meteorite craters in the depths.

New craters are easiest to spot in flat and dusty areas, but “this type of terrain covers less than half of the Martian surface,” Zenhaeusern said.

“However, the sensitive InSight seismometer could hear every single impact within range of the landers,” she added.

The scientists tracked a specific acoustic signal created when meteorites hit Mars to estimate the diameter of the craters and their distance from InSight.

They then calculated the number of craters that had formed near the lander within a year and extrapolated this number to the entire planet.

“This is the first work of its kind to use seismological data to determine how often meteorites hit the surface of Mars,” said Domenico Giardini, who works on the InSight mission.

This data should be taken into account when “planning future missions to Mars,” he added.

The researchers estimated that about once a month a large meteorite impact creates a 30-meter-wide crater on Mars – a thought that may stick in the minds of astronauts hoping to one day walk on the red surface.

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