Geological characteristics of China's Tianwen-1 landing site at Utopia Planitia, Mars

Abstract China's first Mars mission Tianwen-1 successfully touched down the surface of the southern Utopia Planitia on 15th May 2021. In this study we investigate the geological characteristics of the target landing site (Site 1) and a backup landing site (Site 2) on Utopia Planitia for Tianwen-1 Mission. Site 1 is located in a topographic low and generally flat area to the southern Utopia basin, while Site 2 is located in the Utopia-Elysium transition zone. Several geological features indicative of the presence of a large reservoir of volatiles are identified and mapped in detail for both landing sites, including pitted cones, giant polygons, rampart and pancake craters. The volcanism-related morphologies, e.g., lava flows, lahars, and dikes, are also mapped for Site 2. The compositional analysis reveals little exposures of hydrous materials due to dust cover and/or lacking of data coverage over the regions. Crater counting analysis showed that the Site 1 has an absolute model age of ~3.68 Ga and ~3.45 Ga when including and excluding ghost craters, respectively. The absolute model age of Site 2 is ~3.34 Ga. Finally, the evolutionary history of the Utopia Planitia is discussed, and the related scientific hypotheses to be tested for the in situ exploration are suggested. Our study provides a framework for the Tianwen-1 in situ exploration, which will impose important constraints on the nature and evolution history of the northern lowlands.