It is understood that today there is still water and ice on Mars and its surface shows the existence of ancient oceans, lakes, rivers and rivers. But the pressure and temperature conditions are such that we also detect dry ice, that is to say carbon dioxide (CO2) frozen and particularly at the polar ice caps.
Some very recent flow traces monitored by orbiting probes such as Mars Reconnaissance Orbiter (MROMRO) of NASA with the now legendary camera High Resolution Imaging Science Experiment (HiRise) are perhaps the product during Martian summers and low latitudeslatitudes melting of dry ice deposits.
In fact, even in the last billion years of Martian history, it is not certain that some of the dry river and lake beds on Mars, which indicate the presence of flows long ago , is not the product of significant quantities of carbon dioxidecarbon dioxide liquidliquid on the surface, quantities that have now disappeared, like liquid water, and we don’t really know where or how with certainty.
THE geologistsgeologists Martians nevertheless pointed out a long time ago that several deposits of mineralsminerals and the rocks they form, detected both from space and with Mars roversMars roversare clearly associated with liquid water, H2O therefore and not CO2).
After 1,000 days of Martian exploration, NASA’s Perseverance rover is studying rocks that bear witness to several eras in the history of a billion-year-old river delta. Scientists are studying this region of Mars, known as Jezero Crater, to see if they can find evidence of ancient life recorded in the rocks. Perseverance Project Scientist Ken Farley offers a guided tour of a richly detailed panorama of the rover’s location in November 2023, taken by the Mastcam-Z instrument. Made up of 993 individual images and 2.38 billion pixels, this 360-degree mosaic looks in all directions from a location the rover’s science team calls ” Airey Hill “. Parts of the rover itself are visible in the scene, appearing more distorted towards the edges due to image processing. Color enhancement applied to the image increases contrast and accentuates color differences. By approximating what the scene would look like under Earth-like lighting conditions, this adjustment allows mission scientists to use their daily experience to interpret the landscape. The view on Mars would be darker and more reddish. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Automatically translate”. Choose “French”. © NASA, JPL-Caltech, ASU, MSSS; ESA, DLR, FU-Berlin
Geological sequestration of carbon dioxide, a model for Mars?
However, an article recently published in Nature Geoscience (and the content of which we can partly know due to a poster presented during the tenth international conference on Mars from July 22 to 25, 2024 at California Institute of Technology (Caltech) in Pasadena, California) brings new pieces to the debate. It accompanies an MIT release with comments from Michael Hecht, principal investigator of the Moxie instrument aboard the Mars rover PerseverancePerseverance of NASA and also stationed at the Haystack Observatory at MIT. Hecht explains: “ Understand how enough liquid water could have originally flowed onto Mars to explain the morphologymorphology and the mineralogy we observe today is probably the greatest unresolved question in Martian science. There is probably no single right answer, and we are simply suggesting another possible piece of the puzzle. »
He and his colleagues now have study results regarding the geological sequestration on Earth of liquid carbon dioxide (LCO2). It turns out that in this form, CO2 gives reactions with rocks which produce the same alteration products predominant on Mars, carbonates, phyllosilicatesphyllosilicates and sulfates, which we know come from flows and the presence of liquid water on Earth.
As the MIT press release explains, “ the argument for the probable existence of CO2 liquid on the Martian surface is not an all-or-nothing scenario. The LCO2liquid water or a combination of the two can account for geomorphological and mineralogical evidence for the existence of a Martian surface sculpted by flows ».
However, researchers warn. Indeed, the data revealed by experiments on Earth were obtained under terrestrial temperature conditions and at pressures of several tens ofatmospheresatmospheres. These are very different conditions that have existed on Mars for a few billion years. Which makes Michael Hecht say that “ It is difficult to say how likely it is that these speculations about early Mars are true. What we can say, and we do say, is that the probability is high enough that the possibility should not be ignored ».
