About 3.7 billion years ago, stable rivers up to several meters deep could exist on Mars, according to a new study published in Nature. This was indicated by photographs of layered rocks on the walls of the Hellas crater, taken by the Mars Reconnaissance Orbiter probe.
The Hellas basin, located in the Martian southern hemisphere, has long been of interest to planetologists. This is one of the largest impact craters in the solar system with a height difference between the edges and the bottom of more than 9 thousand meters. The various landforms that have been preserved to this day indicate the presence of a network of ancient rivers, deltas and outflow channels on ancient Mars, and mineral substances indicate that the region once had a very large lake. However, detailed descriptions of alluvial deposits of the Noah period, which began 4.5 billion years ago and lasted about 1.1 billion years, still did not exist.
Francesco Salese’s group from the University of D’Annunzio focused in their study on a rocky cliff about 200 meters high in the northwestern part of the Hellas crater. It is located inside the strike structure with a diameter of about 2000 kilometers, where plains are also located, which contain sedimentary rocks of the Noah era, rich in phyllosilicates of magnesium and iron. The researchers studied the images taken by the HiRISE camera installed on board the Mars Reconnaissance Orbiter, and the MOLA laser altimeter data on the topography of the area, and then built a digital terrain model. Planetologists have compared this model with the relief forms found on our planet.
Due to the fact that the researchers were able to recreate in detail the relief of a rocky cliff, they were able to discern layered rocks on its slopes and channel forms. They were very similar to sedimentary rocks on Earth, which are formed in the presence of water flows. A topographic analysis of the area showed that probably about 3.7 billion years ago, rivers up to three meters deep flowed in the Hellas crater. Their channel was constantly shifting, resulting in the formation of sandbanks, which scientists were able to see. At the same time, the Salese group notes that these rivers were permanent – according to the authors, they existed for tens or even hundreds of thousands of years. Therefore, sedimentary rocks of this period can be a promising goal for finding evidence of ancient life on Mars.
The work of scientists is further evidences that billions of years ago, conditions on the Red Planet were much more favorable than today. So, in the past, researchers showed that water flows resumed on the surface of Mars from 3.6 to 1 billion years ago, and there was enough hydrogen on it to support underground life for hundreds of millions of years.