Mapping Stepped Scalloped Terrain in the Utopia Planitia at Meter Scale: Implications for Amazonian Climate and Habitability of the Mars

Surface and subsurface ice in the mid-latitudes of Mars is a vital water reservoir, and its distribution and volume are controlled by obliquity-driven climate change. Periglacial landforms, formed in areas where ice thaws on a seasonal timescale, can indicate the distribution and evolution of ice on Mars. Among these landforms, scalloped depressions, which are characterized by rimless, shallow depressions with asymmetric shape, have attracted high attention owing to their thermokarst-like origin and asymmetric morphology.  This study mapped scalloped terrain in the Martian northern lowlands at meter scale and explored its implications for Amazonian climate and habitability. We used CTX mosaics to generate a meter-scale map of scalloped terrain, and found that scalloped depressions are mainly distributed in the Utopia Planitia. These depressions in Utopia Planitia exhibit unique stepped lineae within the depressions compared to those in the southern hemisphere.  Detailed geological investigation of 926 large depressions (>20 km²) revealed that 218 contain stepped lineae, forming staircase profiles that point to multiple episodes of equatorward degradation. Bisides, expanded craters with thermokarst modifications were also observed, providing another trigger for the formation of scalloped depressions and supporting sublimation-driven ice degradation. These landforms are sensitive records of recent high-obliquity events on Mars and provide crucial clues to the planet’s climatic changes, water resource distribution, and potential habitability during the Amazonian period.