Four billion years ago Mars was a very different planet from the red sand desert that we know today. In fact, he had a dense atmosphere, a warm climate and wide availability of surface liquid water. Even a real ocean, with sandy beaches whose remains today are buried at tens of meters deep in the Martian subsoil, as Zhurong Chinese probe discovered, thanks to a series of radar measurements analyzed recently in a study published in the Proceedings of the National Academy of Sciences.
The radar images were taken from the Chinese rover in 2021 during its one -year mission in the area south of Utopia Planitia, the main impact basin of Mars, considered by many scientists the possible seat of an ocean in the distant past of the planet. Rover used a tool known as Ground Pietrating Radar (GPR), capable of probe the subsoil up to a depth of 80 meters, and to identify the presence of salient characteristics, such as the border between different layers of rock.
This is how the authors of the study, a team of American and Chinese researchers, managed to identify a often layer of rock with a peculiar form, which winded for all the almost two kilometers crossed by the rover along what the satellite images made it hypothesized represented the ancient shore of a Martian Ocean who disappeared today. With the radar images, the researchers were able to calculate even the size of the particles that make up the rocky layer, identified as well as grains of sand. The composition would therefore have been compatible with that of the dunes formed by the wind on the surface of Mars, but the shape of the deposit left the researchers perplexed.
“Those structures did not seem to be sandy dunes – confirms Michael Manga, researcher of the University of California who contributed to the study – and it is at that point that we started thinking about an ocean. The orientation of the structures is parallel to what the ancient shore would have had. Orientation and slope are therefore perfect for supporting the idea that there has been an ocean for a long period of time, and that this has created sandy beaches “.
To create beaches, however, a large basin of water is not enough. Sedes are needed, and rivers that transport them to the sea and redistribute them along the coasts. “The presence of these deposits implies that at least a good part of the planet must have been hydrogeologically active for a prolonged period of time, in order to supply this coast of water, sediments and potential nutrients,” explains Benjamin Cardenas, of the Pennsylvania State University. “The coasts are usually a great place to look for traces of ancient life forms. It is believed that the first forms of life on earth were born in a place similar to this, between air and low waters “.
It is not the first time that credible evidence of the presence of liquid water basins on the surface of Mars are identified. For example, Perseverances found them in Jezero’s crater. And Curiosity has done the same recently in the Gale crater. In both cases, however, there would be remains of ancient lakes, and not of great oceans such as the one discovered thanks to the data of the Chinese probe.