The Christmas of the stars… Scientists who observe the planet Mars received a remarkable gift last year.
On December 24, 2021, a meteorite hit its surface, causing tremors of magnitude 4. These were detected by the Insight probe and its seismometer, which landed on Mars almost four years ago, some 3,500 kilometers from the place of the impact.
But the origin of this Martian tremor was only confirmed later, by the spacecraft called Mars Reconnaissance Orbiter (MRO).
In orbit around the planet, it took pictures of the newly formed crater within 24 hours of the event.
The image is impressive: blocks of ice were thrown on the surface, and a crater about 150 meters in diameter and 20 meters deep was dug - the largest ever observed since the commissioning of the orbiter MRO, sixteen years ago.
“The big impact [never] listened to”
Even though meteor impacts on Mars are not uncommon, "we never thought we'd see something this big," Ingrid Daubar, who works on the Insight and MRO missions, told a news conference on Thursday. .
The researchers estimate that the meteorite itself must have been around 12 meters - which on Earth would have caused it to disintegrate in the atmosphere.
NASA has announced the discovery of an unprecedented meteorite impact on the planet Mars.
This announcement is based on observations made by the InSight landing module on the planet.
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"It is quite simply the biggest impact of a meteorite on the ground that has been listened to since we have been doing science with seismographs or seismometers", explained to AFP Philippe Lognonné, professor of planetology who participated in two studies from those observations, published Thursday in the journal
Science
.
An audio recording of the earthquake, obtained by accelerating the vibrations collected by the seismometer in order to make them audible, was released by NASA.
A “surprising” ice cream
The valuable information collected should help refine knowledge of the interior of Mars, and the history of its formation.
The presence of ice, in particular, is “surprising”, underlined Ingrid Daubar, also co-author of the two studies.
“It's the hottest spot on Mars, closest to the equator, where we've seen ice.
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In addition to the scientific interest of this discovery for the study of the Martian climate, the presence of water at this latitude could prove to be “very useful” for future explorers, declared Lori Glaze, director of planetary sciences at NASA.
“We would like to land astronauts as close to the equator as possible,” she said, due to warmer temperatures.
However, the ice present on site could then be transformed into water or oxygen.
Detection of more than 1,300 “Marsquakes”
The impact of the meteorite was powerful enough to generate both body waves (propagating to the core) and surface waves (crossing the planet's crust horizontally) - thus making it possible to study details the internal structure of Mars.
The crust on which Insight is located was thus found to be less dense than that traversed from the site of the collision.
In addition, the current models "on the deep structure of the mantle of Mars deserve to be re-analyzed a little" in the light of these data, explained Philippe Lognonné, of the Institute of Earth Physics in Paris (IPGP).
As expected, the Insight probe is now operating in slow motion due to dust that has accumulated on its solar panels.
Contact will likely be lost within "about four to eight weeks," said Bruce Banerdt of NASA's Jet Propulsion Laboratory on Thursday, who said he was "sad" but welcomed the mission's success.
Insight has detected more than 1,300 "Marsquakes" in total - including some caused by smaller meteorites - and the data collected will be used by scientists around the world for many years to come.
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