10:45 AM - 12:15 PM
[MIS20-P01] Assessment of brine-related formation mechanism for Dark Dune Spots observed at Martian high latitudes
Keywords:Mars, High-latitude region, Dark Dune Spot, Liquid brine
We visually investigated over 5,000 satellite images of HiRISE (High-Resolution Imaging Science Experiment: 1 pixel about 30 cm) obtained in the high latitude region of Mars (70° to 85°N) around the circumpolar dune field. As a result, we found a wide distribution of dark color landforms called Dark Dune Spot (DDS) appearing from spring to summer (e.g., Gánti et al., 2003) in the 75°-85°N area. We classified the DDS into two types; (1) dark color liquid flow-like structure on the dune slope region, and (2) subcircular structure in which the light color area surrounds the dark color area in the interdune region. In the dune slope region, the dark color streaks grew liquid-like and emanated during early summer, and changed to light color during mid to late summer, suggesting the salt precipitation by evaporation (Kereszturi et al., 2011). On the other hand, in the interdune region, dark color areas extended from the center to the margin during mid to late summer, suggesting that interfacial liquid may be involved (Kereszturi et al., 2012). The distribution of DDS revealed by our survey is in good agreement with the estimated distributional area of perchlorate (Li et al., 2022), suggesting that liquid brine may be involved in the DDS formation.
We also identified that there are many characteristic polygonal landforms at the bottom of the crater, called the Crater-Floor Polygon (CFP) in the 70°-75°N area. Since this polygon landform has an appearance similar to desiccation polygons found in dry lakes on Earth (El-Maarry et al., 2014), liquid water may have existed in the past. Our exploration of the high latitudes of Mars has revealed a wide distribution of landforms such as DDS and CFP, suggesting the possible involvement of liquid brine. In order to verify whether both landforms involve liquid brine, we are conducting a remote sensing survey using CRISM to see if spectral absorptions of perchlorate and chlorine are observed in the distribution areas of both landforms.