Mars : que nous a appris Curiosity depuis son arrivée sur la Planète rouge il y a 10 ans ?

Mars : que nous a appris Curiosity depuis son arrivée sur la Planète rouge il y a 10 ans ?

Six wheels, ultra-precise instruments and hundreds of successful experiments. The Curiosity rover mission (an “astromobile” in Molière’s language) celebrates, on Saturday, August 6, its ten years of activity, since its deployment on Mars by NASA in 2012. On its way, the 900 kg machine He took thousands of snapshots and probed the Martian soil with one question in mind: Was the Red Planet ever habitable? “Affirmative”answer the scientists, who have nevertheless made many other discoveries, 78 million kilometers from Earth.

Mars was habitable… about 3.5 billion years ago

This is the main lesson of the Mars Science Laboratory (MSL) mission, the project that surrounds Curiosity: the Red Planet offered (a long time) ago the conditions conducive to the appearance of life. To reach this conclusion, the scientific teams piloted the robot remotely, in order to scrape, scan, but also drill into the Martian soil. “Little holes, little holes…”amused the National Center for Space Studies (Cnes) in early 2020, referring to the song The Lilac Striker, by Serge Gainsbourg. Small holes, certainly, but rich in discoveries. In fact, these wells made it possible to detect the presence of sulfur, oxygen, phosphorus or even carbon. “essential for life”explains NASA on its website*.

A centimeter-deep drilling by Curiosity on Mars.  (NASAJPL-CaltechMSSS)

“It is the most significant discovery, because it touches the great question of life”explains to franceinfo astrophysicist Sylvestre Maurice, who participated in the development of “ChemCam”, an instrument designed in part by teams from the Institute for Research in Astrophysics and Planetology (IRAP) and Cnes in Toulouse (Haute-Garonne).

Integrated by Curiosity, this system allows analyzing the chemical composition of a rock without moving the robot, thanks to a pulsed laser. “In ten years, we have fired 900,000 shots (of the laser), the scientist proudly summarizes, all this from Toulouse and Los Alamos (United States)”. Because to operate the Curiosity robot, the scientists of the MSL mission are in constant communication.

“You have to notify when you want to ask for a laser shot, a shovel… It’s like driving a car with 60 people, all from a distance.”

Sylvestre Maurice, astrophysicist

in franceinfo

Another significant finding: Curiosity detected a large number of organic molecules thanks to the SAM mini-laboratory, also operated from Toulouse. But beware, these molecules do not prove that there were or still are living beings on Mars. just show that “The basic ingredients were there to support a simple life form 3 billion years ago,” points out Valérie Mousset, MSL project manager at Cnes, who adds that “All the chemical compounds found in our DNA are also present on Mars”. However, this investigation of the traces of Martian life is not the work of Curiosity, but of of its little sister, Perseverance, a rover that has been roaming the surface of Mars since February 2021.

Water in liquid form has long flowed over the Red Planet

An essential component of life as we know it on Earth, water was at the center of all concerns during Curiosity’s launch. Since then, various clues have suggested that streams, or even freshwater rivers, were once part of the Martian landscape. Pebbles, spotted by the rover, whose rounded shape could thus be due to a long journey through the bottom of a river, advances NASA *.

But also deposits of solidified mud, detected at the bottom of what appear to be dry riverbeds. “This is what justified the choice of the landing site (from Curiosity), Olivier Gasnault, the current manager of the ChemCam instrument at Cnes, explains to franceinfo. The rover was sent to what was a more or less closed lake (…) to confirm hypotheses that had been formulated for several decades.

A 3D stereo view of rounded pebbles (image center), taken by the Curiosity rover on Mars on May 20, 2013. (NASA/JPL-Caltech/MSSS)

Curiosity also allowed us to learn more about the characteristics of Martian water, which was “neither too acidic nor too basic”, explains Valérie Mousset, with a temperature rated as “neutral” She too. Even the presence of clay and a relatively low level of salt lead NASA* to say that this water “was fresh and potentially drinkable”. Before changing form, there are more or less 2 billion years.

An unprecedented view of the surface of Mars

All of these discoveries were made possible by careful observation of the Martian environment, including Grace to 17 cameras aboard the rover that provide views in all directions. Since arriving on Mars, Curiosity has traveled just over 28 km, an average distance of 7.6 m traveled each day. Yellowknife Bay, the Pahrump Hills, the Murray Buttes or the foothills of Mount Sharp: these are the mysterious places the rover traveled through. A scientific walk immortalized by more than 500,000 photos, including some selfies in front of unusual rocks.

On the rover’s mast, a part often described as the machine’s head, the MastCam is, for example, capable of taking color photos and videos, as well as 3D stereo images. Thanks to special filters, this sensor can even highlight the composition of certain rocks. Curiosity also has the Mars Hand Lens Imager (MAHLI), the equivalent of a magnifying glass attached to the end of a robotic arm, capable of observing elements as fine as a human hair. From landscape photos to details of a meteorite found along the way*, Curiosity continues to deliver an amazing view of the Red Planet.

We know more about how a planet becomes uninhabitable

Capable of probing the ground and scanning the sky, Curiosity has made it possible to better understand the extreme harshness of the Martian environment. “This planet, which is the same age as Earth, has undergone colossal climatic and geological changes”, emphasizes Sylvestre Maurice. A gravity three times weaker than Earth’s and a persistent cold (-63°C on average) make the Red Planet a frozen and inhospitable desert. But this has not always been the case. Thanks to Curiosity, scientists on the MSL mission realized that Mars’ atmosphere was much thicker in the past, before seeing gaseous masses as well as their water reserves evaporate into the vacuum of space.

“That is precisely what we are beginning to study now and for the next three years, olivier Gasnault Point, that is, the transition from the wettest period to the driest period on Mars, which appears to have occurred in the form of long cycles.” Scheduled to last between two and six years, the Curiosity rover far exceeded the expectations of the engineers who designed it. “Everything we discovered in recent years is just a bonus”Sylvestre Maurice rejoices. And even if the robot is in poor shape, with badly damaged wheels in particular, NASA and its partners (including Cnes) would like to be able to pilot it until at least 2025.

A wheel from the Curiosity rover on Mars on Jan. 27, 2022. (NASA/JPL-CALTECH/MSSS)

Essential information for future manned missions has been collected

Among Curiosity’s great discoveries about the Martian environment, researcher Olivier Gasnault retains one last, capital for future exploration missions. “We now know that radiation levels on Mars are higher than on Earth, which is dangerous for humans.stresses the scientist. A mission to Mars corresponds to the maximum dose of radiation established by NASA for the entire career of an astronaut.

But shields are being prepared, and Curiosity is being placed “under certain hills”, scientists have already noticed a slight drop in these radiations. Enough to reinforce the dream of a manned mission, after the successful deployment of satellites, several rovers and even a mini-helicopter around a planet Mars that has definitely not finished revealing its secrets.

*Links marked with an asterisk refer to publications in English


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