A selfie taken by the Zhurong rover next to its landing pad, captured with a wireless camera. Photo credit: China National Space Administration
The Rover Zhurong, part of China’s Tianwen-1[{” attribute=””>Mars mission, has found evidence of liquid water at low Martian latitudes, indicating potentially habitable environments. This discovery, contradicting previous beliefs that water could only exist in solid or gaseous states on Mars, was made by analyzing morphological features and mineral compositions of dunes in the landing area.
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 led by Prof. Xiaoguang Qin from the Institute of Geology and Geophysics (IGG) of the Chinese Academy of Sciences (CAS).
The study was published on April 28 in the journal Science Advances.
Researchers from the National Astronomical Observatories of CAS and the Institute of Atmospheric Physics of CAS were also involved in the study.
Water traces on bright sand dunes. (a) Topographic contour map of the environs where the trace is located. The coordinate system is east-north-up (ENU) local Cartesian coordinate and the origin is that of the rover coordinate system. The background Digital Orthophoto Map (DOM) photo was taken by NaTeCam. (b) MSCam bird’s-eye-view photo showing a strip-like trace and a likely water-soaked fragmented soil block. (c) Enlarged photo showing polygonal cracks and bright polygonal ridges. (d) Enlarged photo showing circular region with the strip-like trace as a part. (e) NaTeCam 3D image of an interdune depression between two dark longitudinal dunes. (f) A cross-section of the dune along the profile of the white dash line in (e). Credit: IGGCAS
Previous studies have provided proof of a large amount of liquid water on early Mars, but with the escape of the early Martian atmosphere during the later period, the climate changed dramatically. Very low pressure and water vapor content make it difficult for liquid water to sustainably exist on Mars today. Thus, it has been widely believed that water can only exist there in solid or gaseous forms.
Nonetheless, droplets observed on the Phoenix’s robotic arm prove that salty liquid water can appear in the summer at current high latitudes on Mars. Numerical simulations have also shown that climatic conditions suitable for liquid water can briefly occur in certain areas of Mars today. Until now, though, no evidence has shown the presence of liquid water at low latitudes on Mars.
Now, however, findings from the Zhurong rover fill the gap. The Zhurong rover, which is part of China’s Tianwen-1 Mars exploration mission, successfully landed on Mars on May 15, 2021. The landing site is located at the southern edge of the Utopia Planitia (UP) Plain (109.925 E, 25.066 N), where the northern lowlands unit is located.
Researchers used data obtained from the Navigation and Terrain Camera (NaTeCam), the Multispectral Camera (MSCam) and the Mars Surface Composition Detector (MarSCoDe) on board the Zhurong rover to study the different surface features and material compositions of dunes in the Dunes examine landing site.
They found some important morphological features on the dune surfaces, such as crusts, cracks, granulations, polygonal ridges and a streak-like track. Analysis of the spectral data revealed that the surface layer of the dune is rich in hydrated sulfates, hydrated silica (particularly Opal-CT), trivalent iron oxide minerals (particularly ferrihydrite), and possibly chlorides.
“From measured meteorological data from Zhurong and other Mars rovers, we concluded that these dune surface features are related to the involvement of liquid saline water formed by the subsequent melting of frost/snow falling on the saline dune surfaces as they cool,” said Prof Qin.
Salts in dunes in particular will melt frost/snow at low temperatures to form salty liquid water. As the saltwater dries, the precipitated hydrated sulfate, opal, iron oxide, and other hydrated minerals cement sand particles to form sand aggregates and even a crust. Then the crust is further broken up by shrinkage. The later frost/snow melting process continues to form polygonal ridges and a stripe-like track on the crustal surface.
The estimated age of the dunes (about 0.4–1.4 million years) and the relationship between the three water phases suggest that the transfer of water vapor from the polar ice sheet towards the equator during the great tilting stages of Mars’ late Amazon period led to it repeated humid environments at low latitudes. Therefore, a water activity scenario has been proposed, i.e., cooling at low latitudes during the major tilt stages of Mars causes frost/snow to fall and subsequently leads to the formation of crusts and aggregates on the saline dune surface, solidifying the dunes and leaving traces of the Activity of liquid salt water.
The discovery provides important observational evidence for liquid water at low latitudes on Mars, where surface temperatures are relatively warmer and more conducive to life than at high latitudes.
“This is important for understanding the evolutionary history of the Martian climate, searching for a habitable environment, and providing important clues for the future search for life,” said Prof. Qin.
Reference: “Modern Low-Latitude Water on Mars: Possible Evidence of Dune Surfaces” by Xiaoguang Qin, Xin Ren, Xu Wang, Jianjun Liu, Haibin Wu, Xingguo Zeng, Yong Sun, Zhaopeng Chen, Shihao Zhang, Yizhong Zhang, Wangli Chen , Bin Liu, Dawei Liu, Lin Guo, Kangkang Li, Xiangzhao Zeng, Hai Huang, Qing Zhang, Songzheng Yu, Chunlai Li and Zhengtang Guo, April 28, 2023, scientific advances.
DOI: 10.1126/sciadv.add8868
#Chinas #Zhurong #Mars #Rover #finds #evidence #water #Martian #sand #dunes
