Mars: What has Curiosity taught us since its arrival on the red planet 10 years ago?


Six wheels, ultra-precise instruments and hundreds of successful experiments. The mission of the Curiosity rover (an “astromobile” in the language of Molière) celebrates, on Saturday, August 6, its ten years of activity, since its deployment to Mars by NASA in 2012. In the On its way, the 900 kg machine 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, however, have 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 surrounding Curiosity: the red planet offered favorable conditions for the (very) long time ago ‘appearance of life. To reach this conclusion, the scientific teams piloted the robot remotely, in order to scrape, scan, but also drill the Martian soil. “Little holes, small holes…” laughed the National Center for Space Studies (Cnes) at the beginning of 2020, referring to the song Le poinçonneur des Lilas, by Serge Gainsbourg. Small holes, certainly, but rich in discoveries. In fact, these soundings have made it possible to detect the presence of sulphur, oxygen, phosphorus or even carbon, “essential for life”, explains NASA on its website*. A perforation a few centimeters deep made by Curiosity on Mars. (NASAJPL-CaltechMSSS) “This is the most significant discovery, because it touches on the great question of life,” 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 de Tolosa (Haute-Garonne). Incorporated by Curiosity, this system makes it possible to analyze the chemical composition of a rock without moving the robot, thanks to a pulsed laser. “In ten years we have performed 900,000 (laser) shots,” the scientist proudly sums up, all this from Toulouse and Los Alamos (United States). Because to make the Curiosity robot work, MSL mission scientists are constantly communicating. “You have to give notice when you want to order a laser shot, a shovel… It’s like driving a car with 60 people, all at a distance.” Sylvestre Maurice, franceinfo astrophysicist Another important finding: Curiosity detected a large number of organic molecules thanks to the SAM minilaboratory, also operated from Toulouse. But beware, these molecules do not prove that there was or still is life on Mars. They simply show that “the basic ingredients were there to support a simple form of life 3 billion years ago,” says Valérie Mousset, head of the MSL project at Cnes, who adds that “all the chemical compounds found in our DNA are also present.” on Mars.” This investigation of traces of Martian life is not the work of Curiosity, however, but of its little sister, Perseverance, a rover that has been roaming the surface of Mars since February 2021. Water in liquid form is time that flows over the red planet. An essential component of life as we know it on Earth, water was at the center of every concern during Curiosity’s launch. Since then, several clues have suggested that the streams, or even freshwater rivers, became part of the Martian landscape. Pebbles, detected by the rover, whose rounded shape could therefore be due to a long journey to the bottom of a river advance the NASA*. But also deposits of solidified mud, detected at the bottom of what appears to be a dried river bed. “This is what justified the choice of the landing site (of Curiosity), explains to franceinfo Olivier Gasnault, the current manager of the ChemCam instrument at Cnes. The rover was sent to what was a more or less closed lake (…) in order to confirm hypotheses that have already been formulated for several decades.” A 3D stereo view of rounded pebbles (in the center of the image ), taken by the Curiosity rover on Mars on May 20, 2013. (NASA/JPL-Caltech/MSSS) Curiosity also learned more about the characteristics of Martian water, which was “neither too acidic nor too basic” , explains Valérie Mousset, with a temperature also classified as “neutral”. The presence of clay and a relatively low level of salt even makes NASA* say that this water “was fresh and potentially drinkable”. Before changing shape, there are more or less 2 billion years.Unprecedented visualization of the surface of Mars All these discoveries were possible thanks to the meticulous observation of the Martian environment, in particular thanks to the 17 cameras on board the rover that provide views in all directions Since arriving at M art, 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: it is through these mysterious places that the rover traveled. A scientific walk immortalized by more than 500,000 photos, including a few selfies in front of unusual rocks. On the mast of the rover, a part often described as the head of the machine, 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 objects as fine as a human hair. From landscape photos to details of a meteorite found along the way*, Curiosity continues to provide an amazing panorama of the red planet. We know more about how a planet becomes uninhabitable Capable of probing the ground and also 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 the Earth, has undergone colossal climatic and geological changes,” emphasizes Sylvestre Maurice. Gravity three times weaker than Earth’s and persistent cold (-63°C on average) make Mars an icy 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 and their water reserves evaporate into the vacuum of space. “This is precisely what we are starting to study now and over the next three years, Olivier Gasnault points out, namely the transition from the wettest period to the driest period on Mars, which seems to have taken place 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 have discovered in recent years is just an advantage,” rejoices Sylvestre Maurice. And still that the robot is in poor condition, with the wheels especially badly damaged, NASA and its partners (including Cnes) would like to be able to fly it at least until 2025. A wheel of the Curiosity rover on Mars on January 27, 2022. (NASA / JPL-CALTECH / MSSS) Essential information collected for future manned missions Among Curiosity’s major discoveries in the Martian environment, researcher Olivier Gasnault holds one last, crucial for future missions of exploration.” We now know that the levels of radiation on Mars are higher than on Earth, which is dangerous for humans, the scientist emphasizes. A mission to Mars corresponds to the maximum dose of radiation that NASA sets for the entire career of an astronaut.” But shields are being prepared, and by placing Curiosity “under certain hills,” scientists have already observed a slight drop in this radiation. Enough to strengthen the dream of a manned mission, after the successful deployment of satellites, several rovers and even a mini-helicopter around a planet Mars that definitely does not has finished revealing its secrets.*Links marked with an asterisk refer to publications in English
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