The Zhurong rover, part of China’s Tianwen-1 Mars mission, has found evidence of liquid water in low latitudes on Mars that points to potentially habitable environments. Contrary to previous beliefs that water on Mars could only exist in solid or gaseous form, this discovery was made by analyzing the morphological features and mineral composition of the dunes at the landing site.

According to research led by Professor Xiaoguang Qin of the Institute of Geology and Geophysics (IGG), the Zhurong rover has found evidence of water on the surface of sand dunes on present-day Mars, providing important evidence for liquid water observations at low Martian latitudes. of China. Academy of Sciences (CAS).

Previous studies have provided evidence of abundant liquid water on early Mars, but the climate changed dramatically in the later period as the early Martian atmosphere escaped. The very low pressure and water vapor content make it difficult for liquid water to exist on Mars today. Therefore, it is widely believed that water can only exist there in solid or gaseous form.

Yet the droplets observed on Phoenix’s robotic arm prove that salty liquid water can emerge during the summer months at modern high latitudes on Mars. Numerical simulations have also shown that climatic conditions suitable for liquid water may occur in some parts of Mars today. However, there is still no evidence of liquid water on Mars at low latitudes.

Now, however, findings from the Zhurong rover fill that gap. The Zhurong rover, 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 end of the Utopia Planitia (UP) plain (109.925 E, 25.066 N) where the northern plain is located.

Researchers used data from the Zhurong rover’s Navigation and Terrain Camera (NaTeCam), Multispectral Camera (MSCam), and Mars Surface Composition Detector (MarSCoDe) to study the landing site’s multi-scale surface features and dune material composition.

They found some important morphological features such as crusts, cracks, granulation, polygonal ridges and a banded track on the dune surface. Analysis of the spectral data showed that the surface layer of the dunes was rich in hydrated sulfates, hydrated silica (especially opal-CT), trivalent iron oxide minerals (especially ferrihydrite), and possibly chlorides.

“Based on the meteorological data measured by Zhurong and other rovers, we conclude that these dune surface features are due to the entrainment of liquid brine formed by the subsequent melting of frost/snow falling onto the salt-containing dune surface as the cooling begins,” said Professor Qin.

Especially salts in sand dunes cause frost/snow melt at low temperatures to form salty liquid water. As the brine dries, the hydrated sulfate, opal, iron oxide, and other hydrated minerals that precipitate aggregate the sand particles to form sand clumps and even crusts. Then the shell cracks without further shrinkage. The subsequent frost/snowmelt process creates polygonal ridges and a band-like mark on the surface of the earth’s crust.

The relationship between the estimated age of the dunes (about 0.4–1.4 million years) and the three water phases suggests that water vapor transfer from the polar ice sheet to the equator occurred during the major tilt phases of Mars’ late Amazonian period. resulted in multiple wet environments at low latitudes. Therefore, a water activity scenario has been proposed, i.e., cooling at low latitudes during the main phases of the Martian tilt causes frost/snowfall and subsequently the formation of crusts and clumps on the surface of the salt dunes, thereby solidifying the sand dunes and separating them from the surface. traces of liquid brine activity.

The discovery provides important observational evidence for the presence of liquid water at low latitudes on Mars, where surface temperatures are relatively high and more habitable than at high latitudes.