China finds, for the first time, evidence of liquid water in the southern plains of Mars

2023-04-28 20:13:58

The Zhurong rover observes crusts, cracks, granulation, ridges and a fringe-like trail that reveal the presence of water in the dunes of the southern plains of the planet

The Zhurong robotic vehicle, part of the Chinese Tianwen-1 mission to Mars, has just found evidence of liquid water in the dunes of the red planet. And it has done it where no one had yet achieved it, in low Martian latitudes, which shows that water is still present today, at least during the warm seasons, in more places on the planet than previously thought.

The study, led by Professor Qin Xiaoguang, from the Institute of Geology and Geophysics of the Chinese Academy of Sciences, has just been published in ‘Science Advances’.

Numerous previous works had already provided evidence that billions of years ago Mars had a large amount of water in the form of seas, lakes and rivers. But after the loss of its primitive atmosphere, which escaped into space, the climate changed drastically and the continuity of Martian water was seriously compromised. For many years, in fact, scientists thought that for many millions of years water can only exist there in solid or gaseous form.

However, the droplets of water that appeared on the long robotic arm of the Phoenix, a mission that landed on Mars in 2008 near the north pole, clearly proved that liquid water can still appear on the red planet during the summer. Simulations made then showed that weather conditions suitable for liquid water can briefly occur in certain areas of Mars even today. But until now no evidence had shown the presence of liquid water at low latitudes on Mars.

Now, the Zhurong findings have filled that void. The rover, which is part of the Chinese exploration mission Tianwen-1, landed on May 15, 2021 at the southern tip of Utopia Planitia. Since then, researchers have used Zhurong’s various instruments to study surface features at different scales and the material compositions of the dunes in the landing area.

water tests

On the surface of the dunes, Qin Xiaoguang and his team discovered some important morphological features: crusts, cracks, granulation, polygonal ridges, and a fringe-like trace. Subsequent analysis of the spectral data revealed that the surface layer of the dune is rich in hydrated sulfates, hydrated silica (especially CT-opal), trivalent iron oxide minerals (especially ferrihydrite), and possibly chlorides.

“Based on meteorological data measured by Zhurong and other Mars rovers,” Qin explains, “we inferred that these dune surface features were related to the involvement of liquid saline water formed by subsequent melting of falling frost/snow. on salt-bearing dune surfaces when cooling occurs.” In other words, the salts in the dunes cause the frost/snow to melt at low temperatures to form salty liquid water.

When the saline water dries, the precipitated hydrated sulfate, opal, iron oxide, and other hydrated minerals cement the sand particles to form aggregates and even crusts. The bark then cracks further from shrinkage. The subsequent frost/snow melting process forms more polygonal ridges and a strip-like trail on the crustal surface.

The estimated age of the dunes (400,000 and 1.4 million years) and the relationship between the three water phases suggest that the transfer of water vapor from the polar ice cap toward the equator led to repeated wet environments at low latitudes. . Therefore, the researchers have proposed a water activity scenario: cooling at low latitudes during the large obliquity stages of Mars causes frost/snow to fall and subsequently results in the formation of crusts and aggregates on the surface. surface of salty dunes, which solidifies the dunes and leaves traces of liquid saline water activity.

The discovery constitutes the first observational evidence for liquid water at low Martian latitudes, where surface temperatures are relatively warmer and more suitable for life than at high latitudes. “This is important -Qin concludes- to understand the evolutionary history of the Martian climate, search for habitable environments and provide key clues for future searches for life.”