MSGID: 1:317/3 63ec5fec   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Complex subsurface of Mars imaged by Chinese rover Zhurong    
      
     Date:   
         February 14, 2023   
     Source:   
         Geological Society of America   
     Summary:   
         Ground-penetrating radar from China's Martian rover Zhurong reveals   
         shallow impact craters and other geologic structures in the top   
         five meters of the red planet's surface.   
      
      
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   FULL STORY   
   ==========================================================================   
   Ground-penetrating radar from China's Martian rover Zhurong reveals   
   shallow impact craters and other geologic structures in the top five   
   meters of the red planet's surface. The images of the Martian subsurface   
   are presented in a paper published in Geology Thursday.   
      
      
   ==========================================================================   
   The Zhurong rover was sent to Mars as part of China's Tianwen-1 mission.   
      
   Launched in July 2020, the rover landed on the surface on 15 May 2021. The   
   rover was sent to a large plain in the northern hemisphere of Mars named   
   Utopia Planitia, near the boundary between the lowlands where it landed   
   and highlands to the south. The region was chosen because it's near   
   suspected ancient shorelines and other interesting surface features,   
   where the rover could look for evidence of water or ice. A large body   
   of underground ice was identified in a nearby part of Utopia Planitia   
   in 2016 by radar from NASA's Mars Reconnaissance Orbiter. After landing,   
   the Zhurong rover traveled about 1.9 km south, taking pictures of rocks,   
   sand dunes, and impact craters, and collecting ground-penetrating radar   
   data along the way.   
      
   Ground-penetrating radar detects features underground by sending   
   electromagnetic pulses into the ground that are reflected back by any   
   subsurface structures it passes over. The Zhurong rover uses two radar   
   frequencies -- a lower frequency that reaches deeper (~80 meters) with   
   less detail, and a higher frequency used for the latest study, which shows   
   more detailed features but only reaches ~4.5 meters down. Researchers   
   hope that imaging the subsurface of Mars will help to shed light on the   
   planet's geologic history, previous climate conditions, and any water   
   or ice the planet may host now or in the past.   
      
   The researchers saw several curving and dipping underground structures in   
   the Martian soil that they identify as buried impact craters, as well as   
   other sloping features with less certain origins. They did not see any   
   evidence of water or ice in the top five meters of soil. Radar images   
   of the deeper structures revealed layers of sediment left by episodes   
   of flooding and deposition in the past, but also found no evidence of   
   water in the present day.   
      
   This does not rule out the possibility of water deeper than the eighty   
   meters imaged with the radar.   
      
   In the new paper, the researchers contrast the data from Mars with ground-   
   penetrating radar previously collected from the moon, which shows a   
   much different shallow subsurface structure. Where the shallow Martian   
   surface contains several distinct features that show up in the radar,   
   the top 10 meters of the moon has fine layers but no evidence of other   
   structures like impact crater walls, despite also being subjected to   
   meteorite bombardment. The walls of impact craters are, however, observed   
   at greater depths on the moon, buried beneath the 10-meter-thick layer   
   of fine debris.   
      
   The difference may be in the atmosphere -- while Mars' atmosphere   
   is a meager 1% of the volume of Earth's, the moon has virtually no   
   atmosphere. With essentially no atmospheric protection, the moon's surface   
   is bombarded by more of the smallest micrometeorites that rework the   
   surface, eroding smaller-scale features and leaving behind fine layers   
   of ejecta. By contrast, the surface of Mars is not being subjected to   
   as many micrometeorite impacts because these smaller objects burn up in   
   the atmosphere. In the regions imaged by Zhurong, burial by wind-blown   
   sediment may have also protected the impact craters from erosion. One   
   of the craters imaged had its rim exposed at the surface, but the other   
   crater was buried.   
      
   Yi Xu, the lead author on the study, explains, "We found a lot of dunes   
   on the surface at the landing site, so maybe this crater was quickly   
   buried by the sand and then this cover reduced space weathering, so we   
   can see the full shape of these craters walls."   
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   ==========================================================================   
   Story Source: Materials provided by Geological_Society_of_America. Note:   
   Content may be edited for style and length.   
      
      
   ==========================================================================   
   Related Multimedia:   
       * Images_of_the_Martian_subsurface   
   ==========================================================================   
   Journal Reference:   
      1. Ruonan Chen, Ling Zhang, Yi Xu, Renrui Liu, Roberto Bugiolacchi,   
      Xiaoping   
         Zhang, Lu Chen, Zhaofa Zeng, Cai Liu. Martian soil as revealed by   
         ground- penetrating radar at the Tianwen-1 landing site. Geology,   
         2023; DOI: 10.1130/G50632.1   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/02/230214153858.htm   
      
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