Seismic measurements show that the planet Mars is hit by hundreds of meteorites every year, five times more than previously thought, according to a study published Friday (28.06.2024) by the journal Nature Astronomy.
In November 2018, NASA’s InSight spacecraft dropped the seismometer on Elysium Planitia, a vast flat region on Mars, allowing us to hear for the first time what is happening on the planet. Previous estimates were based on crater observation models.
“It seems more effective to listen to the impacts than to try to see them if we want to understand how often they occur,” co-author and Professor Gareth Collins of British Imperial College said in a statement.
Between 280 and 360 meteorites per year
The Red Planet receives many more meteorites because it is closer to the Solar System’s main asteroid belt. In addition, it has almost no atmosphere – it is a hundred times thinner than Earth’s – so it cannot rely on this protective shield to disintegrate some of the meteorites.
The new measurements allowed researchers to determine that the planet is hit by between 280 and 360 meteorites each year, creating craters at least eight meters in diameter.
“This rate is five times higher than the number estimated from images taken in orbit alone,” explains Geraldine Zenhäusern, a researcher at the Swiss Federal Institute of Technology Zurich (ETH), in a statement from her institution.
Observation difficulties
Identifying small meteorite craters from an orbiting probe is even more difficult on Mars because sandstorms are common: “The new craters can be seen on flat, dusty terrain, but this type of terrain only covers half of the planet,” says Zenhäusern.
That’s why the advantage of the seismograph was “being able to hear every impact within the range of the probe.”
How the seismograph works
The scientific team identified a particular type of acoustic waves that propagate on the surface of Mars when a meteorite falls. The seismograph detects the so-called Marsquake-VF (High Frequency Mars Earthquakes) which allow the diameter of a crater and its distance from the probe to be estimated.
Then the number of craters created in a year within a certain radius around the probe is calculated and that figure is extrapolated to the scale of the planet: “It is the first study of its type that determines with seismological data the frequency of impacts of meteorites on the surface of Mars,” says ETH professor Domenico Giardini.
JU (afp, efe)
