The Zhurong rover has found evidence of water on dune surfaces on modern Mars by providing key observational proof of liquid water at low Martian latitudes, according to a study.

The discovery, published in the journal Science Advances, provides key observational evidence of liquid water at Martian low latitudes, where surface temperatures are relatively warmer and more suitable for life than at high latitudes.

"This is important for understanding the evolutionary history of the Martian climate, looking for a habitable environment, and providing key clues for the future search for life," said Prof. Qin Xiaoguang from the Institute of Geology and Geophysics (IGG) of the Chinese Academy of Sciences (CAS).

The researchers used data obtained by the Navigation and Terrain Camera (NaTeCam), the Multispectral Camera (MSCam), and the Mars Surface Composition Detector (MarSCoDe) aboard the Zhurong rover to study the different-scale surface features and material compositions of dunes at the landing site.

The landing site is located at the southern edge of the Utopia Planitia (UP) Plain, where the northern lowlands unit is located.

They found some important morphological features on the dune surfaces, such as crusts, cracks, granulation, polygonal ridges, and a strip-like trace.

The analysis of spectral data revealed that the dune surficial layer is rich in hydrated sulfates, hydrated silica (especially opal-CT), trivalent iron oxide minerals (especially ferrihydrite), and possibly chlorides.

"According to the measured meteorological data by Zhurong and other Mars rovers, we inferred that these dune surface characteristics were related to the involvement of liquid saline water formed by the subsequent melting of frost/snow falling on the salt-containing dune surfaces when cooling occurs," said Prof. Qin.

Specifically, salts in dunes cause 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 sand particles to form sand aggregates and even crust.

Then the crust is further cracked by shrinkage. The later frost/snow melting process further forms polygonal ridges and a strip-like trace on the crust surface.

The estimated age of the dunes (about 0.4-1.4 million years) and the relationship among the three phases of water suggest that the transfer of water vapour from the polar ice sheet toward the equator during the large obliquity stages of Mars's late Amazonian period led to repeated humid environments at low latitudes.

The Zhurong rover, which is part of China's Tianwen-1 Mars exploration mission, successfully landed on Mars on May 15, 2021. [IANS/NS]