Past of the hole where perseverance landed intrigues scientists

Arrival of the rickshaw perseverance on Mars, which supplemented the instruments already on site such as Rover Curiosity or the Insight seismic stationmade it possible to explore a new environment on Mars: Jezero Crater.

The first observations made it possible to quickly establish that this crater was occupied by a vast lake, It is fed by a river that forms a delta. The site is therefore particularly suitable for studying the watery history of the Red Planet and searching for possible traces of life. However, these topics require detailed study of geology Place: rock nature, mineralogy, and sedimentary architecture attesting to episodes and conditions LakeAnd the volcanoes…

Waiting for the samples to return to Earth, Operation planned only in 2033however, the analyzes are progressing well from the data migrated by rover. Four new studies have been published together and detail the nature of the soil and subsoil at Jezero crater.

The floor of Jezero crater is composed of igneous rocks of deep origin

During its journey in the heart of the ancient lake, the chariot of perseverance had already conducted many analyzes of the rocks that make up the bottom of the crater. When everyone expects to find sedimentary rocks deposition at the bottom of the lake or volcanic rockslike the old streams washthe data revealed that the crater in fact It is often formed by the accumulation of molten rock. Look for this type of rockbump It’s amazing, because these rocks are called subterraneanmeaning that it usually forms in depth, generally in the core magma chambers Or at the bottom of lava lakes. It actually results from the slow cooling of the silhouette. The crystals that form as the temperature decreases will gradually settle to the bottom of the magma reservoir and accumulate to form stratified rock.

Either way, the presence of this type of rock outcropping at the bottom of the crater can only mean one thing: all of the material that covered it has been removed by the slow process of erosion over the years. billions of years. We are still talking about a rock several hundred meters thick! These results have been published in the journal Science under the title An olivine protrusion accumulated on the floor of Jezero craterMars And also in the article Composition: Stratiform and Density Volcanic Topography of Jezero Crater, Mars featured in science progress.

this is stratification From the basement of Jezero crater it was confirmed by radar images carried out by Perseverance. The instrument carried by the rover has already made it possible to image the interior of the Earth at a depth of about 15 m, revealing a highly stratified structure, which can be explained by the lithic origin of the rocks, but also by the presence of sedimentary lake deposits. These results are presented in the article Ground-penetrating radar observations of subsurface structures in the floor of Jezero crater, MarsPublished in the magazine science progress.

One thing is for sure, the rocks analyzed by the rover attest to a rocky ring before the Jezero Delta formation. So they can make it possible to give a lower bound on the age of this sedimentary formation.

Various effects of weather factors in water

Their discovery is doubly interesting because these rocks also bear weathering by water. The igneous rocks Since the date is particularly easy to determine, samples taken by perseverance can make it possible to establish an accurate chronology of the various aquatic events of the site and in particular for the history of the formation of the lake. This data is one of the key elements that allow a better understanding of the evolution of climate Martian. So studying these rocks could allow us to know exactly when the planet’s climate allowed the creation of a water system at the surface and when the situation changed dramatically towards the cold, dry conditions we observe today.

Perseverance, however, is not in a position to perform such dates. So we will have to wait patiently for the samples to return to Earth. Thanks to the instruments on board the rover, a detailed study of the accumulations at the bottom of the crater is possible. Their mineral analysis shows that it is composed of complex small crystals ofolivine and pyroxene, indicating slow crystallization. But what interests specialists are the effects of water weathering. It seems that the different samples taken by perseverance at different points of the crater have actually changed in different ways.

The rocks of the Moaz site contain in their pores metal which may have consisted of a Salt waterToo salty. On the contrary, rocks from the Sitah site show traces of interaction with carbonate-rich waters. Thus, the two samples attest to a change in lake conditions over time, which may be related to it Climate change. Once again, we will have to wait for the samples to return to Earth so that we can accurately date these different phases and establish their chronology. Analysis details are available in the article Hydrolytic modified igneous rock samples on the floor of Jezero crater, Marspublished in Science.

However, the lack of minerals from the weathering of igneous rocks indicates that the lake’s period of existence was relatively short.

valuable samples

Aside from the very local case of Jezero, a more detailed study of olivine-rich deposits could help to better understand the magmatic activity of Mars. Combined with satellite images, data reported by Perseverance can help paint a broader picture of the planet’s volcanic history.

We better understand the value of samples taken by the perseverance and precautions that scientists in charge of the mission take to ensure to support And their arrival on Earth 11 years later. At each of the four sites studied, the samples taken were repeated. These duplicates will be stored in a backup location near the delta in case the samples held by persistence cannot be recovered, for example due to mechanical failure. At this site will also be stored samples of sedimentary rocks recently collected by the delta-level rover. New samples should also provide us with valuable information about Mars’ past.