Mars is hit by meteorite impacts almost daily, with impacts about five times more frequent than previously estimated, according to seismic recordings made on the Red Planet.
Until now, we have estimated the frequency of these effects using models that combine observations of meteorite craters on the Moon and images of the Martian surface taken by orbiting probes.
We modified these models to match the characteristics of the Red Planet. Mars is much larger than the Moon, much closer to the Solar System's main asteroid belt, and a prime target for large rocks hurtling through space.
Moreover, it is virtually devoid of an atmosphere—its atmosphere is a hundred times thinner than Earth's—and it cannot even rely on this protective shield to break up some meteorites.
An international team led by researchers from the Zurich University of Applied Arts (ETH) and Imperial College London has brought the journal Astronomy Nature Friday posted a new look at the topic, thanks to Audio.
“It seems that hearing about the effects is more effective than trying to see them if we want to understand how often they occur,” Gareth Collins, co-author of the study and a professor at Britain’s Imperial College, said in a press release from his office.
And what could be better than the SEIS (Seismic Experiment of Internal Structures) seismometer, a device produced under the supervision of CNES (National Centre for Space Studies).
NASA's InSight probe placed it in November 2018 on the Martian plain of Elysium, allowing humanity for the first time to press its ear to the planet's ground. The initial goal is to measure its internal activity and potential seismic events.
“Hear every trace”
The team of researchers used this data to determine that the planet is hit by 280 to 360 meteorites every year, creating craters at least eight meters in diameter. “This rate is five times higher than the estimated number of images taken in orbit alone,” explains Geraldine Zenhausern, a researcher at ETH, in a press release issued by her institution.
Identifying small meteorite craters with an orbiting probe is more difficult because the planet is the scene of frequent sandstorms that can mask them.
“If new craters can stand out better on flat, dusty terrain, then this type of terrain only covers half the planet,” according to M.I Zenhausern. The advantage of the seismograph was “the ability to hear every impact within the range of the probe.”
The team's calculations are based on identifying a specific type of sound wave that propagates across the surface of Mars when the meteorite impacts. These events, called Marsquake-VF (Marsquake-VF), allowed them to estimate the diameter of the crater and its distance from the probe.
Then count the number of craters formed in one year within a given radius around the probe, before extrapolating this data to the planetary scale.
“This is the first study of its kind to quantify the frequency of meteorite impacts on the surface of Mars using seismic data,” says Professor Domenico Giardini.
The data, he added, “should be taken into account when planning future missions to Mars.” The planet is hit almost every month by a meteorite that creates a crater at least 30 metres in diameter.
