The InSight seismometer placed on the surface of Mars heard the fall of a meteorite, a first on a planet other than Earth. The crater caused by the impact could even be found afterwards to confirm the discovery.
As its solar panels slowly become covered in dust and its instruments give way one by one, InSight still continues to give small treats to the scientists who decipher its data. Arrived almost four years ago on the surface of Mars, the lander equipped with a seismometer records all the seismic activity that shakes the planet and provides information on the dynamics at play in its bowels.
But that’s not all. A study appeared in Nature Geoscience September 19, 2022 tells us that the probe also detected meteorites. ” We heard meteorite falls with the seismometerexplains Raphaël Garcia, main author and researcher at ISAE-SUPAERO in Toulouse. The data reveals the waves emitted during re-entry into the atmosphere and during impact with the ground. »
This is the first time that meteorite falls have been detected “live” on another planet. What the device recorded were the atmospheric movements caused by passing through the atmosphere, and the seismic waves that occur when the body crashes on the surface. In total, four impacts have been identified, between May 2020 and September 2021. “ It was among the scientific objectives of the missionsays Raphaël Garcia, but we thought we’d identify some sooner. »
Four meteor impacts heard, then seen
Expectations weren’t very high when InSight launched. The scientific team had counted between 0.2 and 20 meteorites per year. But, what is strange is that all the events have been rather close in time, and this, after almost two years of silence. An inexplicable anomaly at the moment, because recording such impacts is rather difficult. As during the day the wind creates noise, the seismometer is a bit embarrassed and struggles to identify other things, so we have to wait until night and until then they have been rather quiet. It could be that the year 2021 was particularly generous for meteorite falls, but this remains to be proven.
In any case, the four identified impacts could be confirmed with certainty, since InSight is not completely alone: it has eyes above it. Since 2005, the Mars Reconnaissance Orbiter probe has been orbiting the red planet and regularly takes images. She was thus able to find the new craters produced by the meteorite falls heard by InSight. ” It is a good example of complementarity between the missionsenthuses Raphaël Garcia, all instruments on the ground and in orbit collaborate to do the same study. There is a verification that was not possible before. “Here, the entire route of the meteorite could be followed with precision, from its re-entry into the atmosphere, until its landing, with images taken before and after the damage. A first on another planet. Even on Earth, this feat could not be achieved only once, in 2007when a meteorite fall was recorded in Peru and a crater was discovered shortly after south of Lake Titicaca.
It must be said that on Earth, meteorites that reach the ground are rarer, because of the thicker atmosphere than on Mars. In addition, we are a little further from the asteroid belt, which makes this type of event even rarer.
A good advertisement for extraterrestrial seismology
Be that as it may, having so much data available is very practical, to verify that the models in place on the atmosphere or the Martian crust are indeed in line with reality. Here, everything went according to plan, which is good news. In addition, the researchers were able to draw a parallel with the Moon and see how the same impact has different consequences because of the composition of the soil. As the Moon is less hydrated, the crust has a greater tendency to fracture during a shock, much more than on Mars.
” Now we know exactly how much energy is needed to create a crater of a certain size, says Raphael Garcia. We have specific measurements that may be applicable on other planets. This is proof that seismology can be used for this type of research. »
Finally, these findings are also a godsend for reanalyzing all the data provided by InSight, which will become increasingly rare in the last months of the mission, as the probe gradually dies. ” We have certainty for these four impactsassures Raphaël Garcia, but there could be many more that we hadn’t identified before. »
In four years, InSight has recorded earthquakes, wind or other tremors, and it is possible that in the midst of all this, a meteorite fall has not been identified as such. Research is underway to make sure. Even one foot in the grave, InSight has not finished being scrutinized by scientists in the years to come.