The Curiosity rover has been studying the geology and climate of the Red Planet since 2012. All this time, it was believed that the American apparatus was studying the bottom of an ancient Martian lake.
Let us explain that when choosing a landing site, scientists are guided by data collected from orbit. Specialists are very careful in choosing where to land the rover. In particular, the bottom of the lake was supposed to tell scientists about whether life once originated in the water that filled the reservoir.
However, despite numerous scientific evidence that water was once present in the surveyed area, experts now conclude that Curiosity has not been studying the bottom of the lake for almost nine years.
Researchers from Hong Kong analyzed what chemical elements the rover found in the collected rock samples during its entire stay on Mars. Scientists came to the conclusion that, most likely, they got into this area with the wind. Only then did they harden under the influence of atmospheric processes. That is, not under a layer of water, as scientists believed all this time.
Using chemical tests, studying the structure and texture of the samples, the team found evidence of erosion (destruction) of the rock, which could only occur in dry conditions.
Researchers believe that most of the sediment collected by the rover consists of airborne dust and volcanic ash. Later weathering of the rock was due to rain or ice melting.
At the same time, a small part of the studied sedimentary rocks still correspond to those that could be found at the bottom of the lake.
From all this, scientists conclude that the water cover in Gale Crater (the area where Curiosity operates) was much more variable than expected. That is, the authors of the work propose to change the theory of the "big lake" in Gale crater to the theory of several small and temporary lakes that regularly appeared there.
The work, published in the scientific journal Science Advances, offers a fresh look at the well-established understanding of how the Martian climate was formed.
For example, over millions of years on the Red Planet, periods of high humidity could be short and frequent. So far, researchers are inclined to believe that the climate on Mars has been humid for one long period of time.
On the left - the distribution of water along the bottom of the crater, according to the old hypothesis, on the right - according to the new one.
Illustration by ESA / HRSC / DLR.
The study authors also propose to revise the generally accepted approach to the analysis of sedimentary rocks.
Of course, researching something that is not only millions of kilometers away, but also happened billions of years ago, is not easy. To pinpoint the origin of rocks in Gale Crater, scientists will need to examine more than one sample collected by the Curiosity rover. And, perhaps, the leading theory of what has happened on Mars since its inception will change more than once.