The arrival of the roveron Mars, which integrated instruments already on site such as or the made it possible to explore a new Martian environment: the Jezero crater.
The first observations immediately made it possible to establish that this crater was once occupied by a vast lake,. The site is therefore particularly suitable for studying the history of the water of the Red Planet and looking for potential traces of life. However, these issues require detailed study of the of the place: nature of the rocks, mineralogy, sedimentary architecture as evidence of the episodes and conditions , …
Waiting for the return of the champions to Earth,, the analyzes are still doing well from the data transmitted by the rover. Four new studies have just been published together and detail the nature of the soil and subsoil of the Jezero crater.
The bottom of the Jezero crater is composed of igneous rocks of deep origin
During its journey into the heart of the old lake, the Perseverance rover carried out several analyzes of the rocks that form the bottom of the crater. When everyone expected to finddeposited on the bottom of the lake or like the old streams of the data revealed that the bottom of the crater actually is . Find this type of rock it is surprising, because these are called rocks that is to say that they usually form deep, generally in the heart of or at the bottom of the lava lakes. In fact, they derive from a slow cooling of the . The crystals that form as the temperature decreases gradually settle to the bottom of the magma reservoir and accumulate to form a layered rock.
In both cases, the presence of this type of rock at the outcrop at the bottom of the crater can only mean one thing: all the material that covered them has been removed by the slow process of erosion over the years, billions of years. We are still talking about a rock thickness of several hundred meters! These results were published in the journal Science under the titleMarch as well as in the article appeared in Science advances.
Thisof the base of the Jezero crater was confirmed by radar images made by Perseverance. The instrument carried by the rover made it possible to film the subsoil at a depth of about 15 meters, revealing a highly stratified architecture, explained by the magmatic origin of the rocks, but also by the presence of lake sedimentary deposits. These results are presented in the article published in the journal Science advances.
One thing is certain, the rocks analyzed by the rover testify to a magmatic episode prior to the formation of the Jezero delta. They could therefore make it possible to give a lower age limit to this sedimentary formation.
Several traces of atmospheric agents by the water
Their discovery is doubly interesting since these rocks also bear traces of atmospheric agents from the water. TheBeing particularly easy to date, the samples taken by Perseverance could therefore allow to establish a precise chronology of the various water events of the site and in particular to date the formation of the lake. These data are one of the key elements that allow a better understanding of the evolution of the Martian. The study of these rocks could therefore allow us to know precisely when the planet’s climate allowed the establishment of a water system on the surface and when the situation has drastically changed towards the cold and arid conditions we observe today.
Perseverance, however, is unable to fulfill such dates. We will therefore have to wait patiently for the samples to return to Earth. Thanks to the instruments on board the rover, it is however possible to study the mounds on the bottom of the crater in detail. Their mineralogical analysis shows that they are composed of small intricate crystals ofand pyroxene, indicating slow crystallization. But what interests specialists most are the traces of atmospheric agents caused by water. The different samples taken by Perseverance in different points of the crater seem in fact to have been altered in different ways.
The rocks of the Máaz site contain in their poreswhich would be formed by a , very salty. In contrast, the rocks at the Seitah site show traces of reaction with carbonate-rich water. The two samples therefore testify to a change in the conditions of the lake over time, to which it could be related . Once again, we will have to await the return of the samples to Earth in order to accurately date these different phases and establish their chronology. The detail of the analysis is available in the article Posted in Science.
The scarce abundance of minerals resulting from erosion of igneous rocks, however, suggests that the lake’s existence period was relatively short.
Aside from the very local case of Jezero, a more detailed study of olivine-rich mounds could help better understand Mars’ magmatic activity. Combined with satellite imagery, the data reported by Perseverance could therefore help paint a larger picture of the planet’s magma history.
We better understand the value of the samples taken by Perseverance and the precautions taken by the scientists in charge of the mission to ensure theirand their arrival on Earth in 11 years. On each of the four sites studied, the collected samples were duplicated. These duplicates will be stored in a backup site near the delta in case the samples held by Perseverance cannot be recovered, for example due to mechanical failure. This site will also store sedimentary rock samples recently collected by the rover at the delta level. New samples that should also provide us with valuable information about the past of Mars.