Astronomy & Space

Tianwen-1: The Zhurong rover discovers water at low latitudes on contemporary Mars.

According to a study led by Prof. Qin Xiaoguang from the Institute of Geology and Geophysics (IGG) of the Chinese Academy of Sciences (CAS), the Zhurong rover has provided key observational proof of liquid water at low Martian latitudes, which means that it has discovered evidence of water on modern Mars’ dune surfaces.

The study also involved researchers from CAS’s Institute of Atmospheric Physics and the National Astronomical Observatories. The review was distributed in Science Advances on April 28.

Studies in the past have shown that early Mars had a lot of liquid water. However, the climate changed a lot when the early Martian atmosphere left during the later period. Liquid water cannot currently exist on Mars sustainably due to its very low pressure and high water vapor content. As a result, it has long been held that water can only exist there as a solid or a gas.

“Based on the meteorological data collected by Zhurong and other Mars rovers, we deduced 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,”

Prof. Qin Xiaoguang from the Institute of Geology and Geophysics (IGG) of the Chinese Academy of Sciences (CAS).

However, the fact that droplets were observed on the Phoenix’s robotic arm demonstrates that salty liquid water can exist in the summer at Mars’ current high latitudes. Additionally, climates suitable for liquid water can briefly exist in some current Mars regions, according to numerical simulations. As of recently, however, no proof has been shown of the presence of fluid water at low spectral resolution on Mars.

Presently, in any case, discoveries from the Zhurong wanderer fill the hole. On May 15, 2021, China’s Tianwen-1 Mars exploration mission’s Zhurong rover successfully landed on Mars. The northern lowlands unit is at the southern edge of the Utopia Planitia (UP) Plain, where the landing site is located (109.925 E, 25.066 N).

The different-scale surface features and material compositions of dunes in the landing area were investigated by the researchers using data from the Zhurong rover’s Navigation and Terrain Camera (NaTeCam), Multispectral Camera (MSCam), and Mars Surface Composition Detector (MarSCoDe).

On the dune surfaces, they discovered important morphological features like polygonal ridges, crusts, cracks, granulation, and a strip-like trace. 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 spectral data analysis.

“As per the deliberate meteorological information by Zhurong and different Mars wanderers, we deduced that these hill surface qualities were connected with the inclusion of fluid saline water shaped by the resulting softening of ice or snow falling on the salt-containing rise surfaces while cooling happens,” said Prof. Qin.

Particularly, the salts in dunes cause snow and frost to melt at low temperatures, resulting in salty liquid water. At the point when the saline water dries, it encourages hydrated sulfate, opal, iron oxide, and other hydrated minerals in concrete sand particles to shape sand totals and even covers. Then the outside layer is additionally broken by shrinkage. On the crust’s surface, the subsequent frost or snow melting process creates additional polygonal ridges and a strip-like trace.

A transfer of water vapor from the polar ice sheet toward the equator during the large obliquity stages of Mars’ late Amazonian period may have resulted in repeated humid environments at low latitudes, according to the estimated age of the dunes (0.4–1.4 million years) and the relationship between the three phases of water. Hence, a situation of water action has been proposed, i.e., cooling at low scopes during Mars’ enormous obliquity stages prompts ice or snow to fall and, in this manner, brings about the development of hulls and totals on the pungent rise surface, consequently hardening hills and leaving hints of fluid saline water movement.

The finding provides crucial observational evidence for the existence of liquid water at low Martian latitudes, where surface temperatures are more conducive to life than at high latitudes.

“This is significant for grasping the transformative history of the Martian environment, searching for a tenable climate, and giving key insights for the future quest forever,” said Prof. Qin.

More information: Xiaoguang Qin et al, Modern water at low latitudes on Mars: Potential evidence from dune surfaces, Science Advances (2023). DOI: 10.1126/

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