«Wind, waves and a lot of sand: a beach suitable for vacations». The description of Benjamin Cardenas, professor at the State University of Pennsylvania (USA,), seems typical of a tripadvisor review, but, surprisingly, describes the coast of Mars 4,000 million ago … of years. An international team of researchers has reviewed radar images taken for a year by Zhurong, China’s first rover on the red planet, and has found the clearest evidence until Mars housed an important mass of water in the past , with Soft swelling sands bathed in the sun. In addition to appearing a dream place, this environment would also have been more habitable for life.
Zhurong, now inactive, landed in May 2021 in an area known as Utopia plan and toured 1.9 kilometers in perpendicular to some escarpes that are believed to be an old Martian coast. The vehicle used a terrestrial penetration radar (GPR), which is used to detect unmarked pipes or tombs, to probe up to 80 meters below the surface. The images showed thick layers of sediment buried along the entire route, almost identical to coastal deposits on the ground that descend on the slope towards the oceans and are formed when the sediments are transported by the tides and waves towards a Great mass of water.
When the team compared the Martian data with radar images of coastal deposits on Earth, they found surprising similarities. The inclination angles of the sediments observed in Mars were very similar to those observed in coastal sedimentary deposits that we know. «The structures do not seem sand dunes, or impact craters or lava flows. That was when we started thinking about the oceans, ”says Michael Manga, from the University of California Berkeley and co -author of the study that this Monday publishes the scientific journal ‘Proceedings of the National Academy of Sciences’ (PNAS).
According to the authors, the existence of beaches implies the existence of a large ocean without ice, although today Mars is too cold for water to flow in a liquid state. It also implies that there were rivers that threw sediments into the ocean, materials that the waves distributed along the beaches.
“We are seeing that the coastal line of this body of water evolved over time,” says Cárdenas. «We tend to think about Mars as a simple static snapshot of a planet, but it was evolving. The rivers flowed, the sediments moved and the earth formed and eroded. This type of sedimentary geology can tell us what the landscape was like, how it evolved and, more importantly, help us identify where we would want to look for past life, ”he adds.
The study also provided new information about the evolution of the Martian environment, which suggests that a warm and humid period conducive to life potentially lasted tens of millions of years. «The coasts are excellent places to seek evidence of past life. It is believed that the earliest life on Earth began in places like this, near the interface between the air and the shallow waters, ”says Cardenas.
“This reinforces the hypothesis that in the past there was habitability in this region of Mars,” says Hai Liu, from the University of Guangzhou and member of the Tianwen-1 mission team, which included the Zhurong explorer.
Last January, other researchers reported the existence of undulations in the sedimentary rocks of the Gale crater bottom, the landing place of NASA’s curiosity rover, which suggests the presence of a body of liquid water that no longer exists and without ice that covers the surface. The Rover Perseverance has also found evidence of a river delta in the Jezero crater, 2,400 km from the Zhurong landing place. But it is believed that both craters were lakes, not oceans.
«To form waves by waves it is necessary that there be a lake without ice. Now we say we have an ocean without ice. And instead of waves, we are seeing beaches, ”says Manga.
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