February 26, 2024

The Zhurong rover detects mysterious polygons beneath the surface of Mars

This article has been reviewed in accordance with Science X’s editorial process and policies. The editors have highlighted the following attributes, ensuring the credibility of the content:

checked

peer-reviewed publication

trusted source

review


An image from China’s Zhurong rover shows the spacecraft’s hardware in the foreground and the Martian terrain in the background. Credit: CNSA

× to close


An image from China’s Zhurong rover shows the spacecraft’s hardware in the foreground and the Martian terrain in the background. Credit: CNSA

China’s Zhurong rover was equipped with a ground-penetrating radar system, allowing it to observe below the surface of Mars. Researchers announced new results from scans of the Zhurong landing site on Utopia Planitia, saying they identified irregular polygonal wedges located at a depth of about 35 meters along the robot’s entire journey.

The objects measure from centimeters to tens of meters in diameter. Scientists believe the buried polygons resulted from freeze-thaw cycles on Mars billions of years ago, but they could also be volcanic, due to cooling lava flows.

The Zhurong rover landed on Mars on May 15, 2021, making China the second country to successfully land a rover on Mars. The beautiful rover, named after a Chinese fire god, explored its landing site, sent back photos – including a selfie with its lander taken by a remote camera – studied Mars’ topography and conducted measurements with its radar. ground penetration (GPR). ) instrument.

Zhurong had a primary mission of three Earth months, but operated successfully for just over an Earth year before going into a planned hibernation. However, there has been no news from him since May 2022.

Researchers from the Institute of Geology and Geophysics of the Chinese Academy of Sciences who worked on the Zhurong data said GPR provides an important complement to orbital radar explorations from missions such as ESA’s Mars Express and China’s own Tianwen-1 probe. They said the in-situ GPR survey can provide critical local details of shallow structures and composition at depths of approximately 100 meters along the rover’s traverse.

Utopia Planitia is a large plain within Utopia, the largest recognized impact basin on Mars (also in the solar system), with an estimated diameter of 3,300 km. In total, the rover traveled 1,921 meters during its lifetime.


a, Topographic map of Utopia Planitia, showing the landing sites of the Zhurong rover, the Viking 2 lander, and the Perseverance rover. The 4 km elevation contour is shown. Four local regions (c – f) with polygonal terrain are marked with white squares. b, The Zhurong rover traverses from Sol 11 to Sol 113 (HiRISE image: ESP_073225_2055). Green segments denote the wedges of buried polygons recognized in Fig. 2 (P1 – P16). Purple segments denote polygon interiors. c–f, Four representative HiRISE images of polygons in Utopia Planitia whose locations are marked in a: PSP_002202_2250 (c), PSP_006962_2215 (d), PSP_002162_2260 (e), and PSP_003177_2275 (f). Note the range of spatial scales for polygon sizes. The average diameters of the polygons shown in c – f are calculated from Extended Data Fig. 6. Credit: HiRISE images: NASA/JPL/University of Arizona.

× to close


a, Topographic map of Utopia Planitia, showing the landing sites of the Zhurong rover, the Viking 2 lander, and the Perseverance rover. The 4 km elevation contour is shown. Four local regions (c – f) with polygonal terrain are marked with white squares. b, The Zhurong rover traverses from Sol 11 to Sol 113 (HiRISE image: ESP_073225_2055). Green segments denote the wedges of buried polygons recognized in Fig. 2 (P1 – P16). Purple segments denote polygon interiors. c–f, Four representative HiRISE images of polygons in Utopia Planitia whose locations are marked in a: PSP_002202_2250 (c), PSP_006962_2215 (d), PSP_002162_2260 (e), and PSP_003177_2275 (f). Note the range of spatial scales for polygon sizes. The average diameters of the polygons shown in c – f are calculated from Extended Data Fig. 6. Credit: HiRISE images: NASA/JPL/University of Arizona.

The researchers, led by Lei Zhang, wrote in their paper published in Nature Astronomythat the rover’s radar detected sixteen polygonal wedges about 1.2 kilometers away, suggesting a broad distribution of similar terrain beneath Utopia Planitia.

These detected features likely formed 3.7–2.9 billion years ago, during the Late Hesperian and Early Amazonian epochs on Mars, “possibly with the cessation of an ancient moist environment. The paleopolygonal terrain, with or without erosion, was subsequently buried” by later geological processes.

Although polygon-type terrain has been seen in several areas of Mars on many previous missions, this is the first time there are indications of buried polygonal structures.

The buried polygonal terrain requires a cold environment, the researchers wrote, which may be related to water/ice freeze-thaw processes in southern Utopia Planitia on early Mars.

“The possible presence of water and ice required for the freeze-thaw process in the wedges could have come from cryogenic suction-induced moisture migration from an underground aquifer on Mars, from airborne snowfall, or from vapor diffusion for deposition of ice pores,” the article said. explains.


Schematic model of the polygonal terrain formation process at the Zhurong landing site. a, The origin of cracks due to thermal contraction on the surface. b, The formation of fissures filled by water ice or soil material, causing three types of polygonal terrain (ice wedge, composite wedge, and sand wedge polygons). c, The stabilization of the surface polygonal terrain in Late Hesperian-Early Amazonia, possibly with the cessation of an ancient humid environment. d, The paleopolygonal terrain, with or without erosion, was later buried by deposition of covering materials in the Amazon. The image of the surface of Mars was acquired by the Navigation and Terrain Camera (NaTeCam). Credit: Zhang et al, from Nature Astronomy (2023). DOI: 10.1038/s41550-023-02117-3

× to close


Schematic model of the polygonal terrain formation process at the Zhurong landing site. a, The origin of cracks due to thermal contraction on the surface. b, The formation of fissures filled by water ice or soil material, causing three types of polygonal terrain (ice wedge, composite wedge, and sand wedge polygons). c, The stabilization of the surface polygonal terrain in Late Hesperian-Early Amazonia, possibly with the cessation of an ancient humid environment. d, The paleopolygonal terrain, with or without erosion, was later buried by deposition of covering materials in the Amazon. The image of the surface of Mars was acquired by the Navigation and Terrain Camera (NaTeCam). Credit: Zhang et al, from Nature Astronomy (2023). DOI: 10.1038/s41550-023-02117-3

Previous research from Zhurong’s radar data indicated that multiple floods during the same period created several layers beneath the surface of Utopia Planitia.

While the new paper indicates that the most likely formation mechanisms would be soil contraction from wet sediments that dried out, producing mud cracks, however, cooling contraction of the lava could also have produced thermal contraction cracks.

Either way, they note that a huge change in Mars’ climate was responsible for the polygon’s formation.

“The underground structure with the cover materials covering the buried paleopolygonal terrain suggests that there was a notable paleoclimatic transformation some time later,” the researchers wrote. “The contrast above and below about 35 meters depth represented a remarkable transformation of water activity or thermal conditions in ancient Martian epoch, implying that there was a climate change at low to mid-latitudes.”

More information:
Lei Zhang et al, Buried paleo-polygonal terrain detected under Utopia Planitia on Mars by Zhurong radar, Nature Astronomy (2023). DOI: 10.1038/s41550-023-02117-3

Diary information:
Nature Astronomy

Leave a Reply

Your email address will not be published. Required fields are marked *