9:30 AM - 9:45 AM
[MIS23-03] Deciphering the Environmental History of Mars; Geological and Geomorphological Perspectives
Keywords:Mars, Habitable environment, Subsurface ice, Terrestrial analog
Mars is considered to have had a thick atmosphere and warm and humid environment conducive to extraterrestrial life about 3.8 billion years ago. However, the present-day Mars has only a thin atmosphere and extremely cold and dry environment. Most of the early liquid water dissipated into space about 3.5 billion years ago, although a significant amount of H2O water seems to remain stored as ice in the polar cap and shallow subsurface at mid-to-high latitudes (Head et al., 2003). In addition, it has been suggested that salt brine may also exist in liquid form at high latitudes today (Rivera-Valentin et al., 2020), and that it may be possible for extant organisms to exist in relation to the brine. Therefore, Mars is an extraterrestrial planet for which the persistence and evolution of habitable environments can be examined. In this presentation, we will introduce our ongoing research attempting to decipher the environmental history of Mars, by focusing on (1) deltas, (2) subsurface ice, and (3) liquid brine.
In Topic (1), we examined the delta topography on the Martian surface and its relationship with ancient sea-level changes using the flume-tank experimental at Nagasaki University. Then, we examined formation ages of each delta topography by the crater counting method. As a result, we found that the deltas formed by sea-level fall are dated to be at about 3.6~3.5 billion years ago, while the deltas formed by water-level rise in the crater are dated to be at about 3.4~3.2 billion years ago. Based on this evidence, we propose the hypothesis that the northern lowland oceans that spread on ancient Mars disappeared by 3.5~3.4Ga and were replaced by an environment with localized lakes.
In Topic (2), we are attempting to estimate the distribution of subsurface ice in the mid-latitude of Mars as a preceding exploration of the Mars Ice Mapper (MIM) project, an international Mars exploration program planned for the early 2030s. In this study, we focused on periglacial landforms (thermal contraction polygons and pingos) formed by the presence of subsurface ice that develop in the permafrost regions of the Earth. For estimating the subsurface ice distribution of mid-latitude Mars, we chose Mongolia, where the boundary between the permafrost and desert belts is located, as an important terrestrial analog site. By applying our findings of the relationship between the shape of periglacial landforms and the permafrost distribution in Mongolia, we were able to estimate the subsurface ice distribution in the mid-latitude of Mars.
In Topic (3), we are attempting to verify the possibility of the existence of liquid brine in the high-latitude regions of Mars. Remote-sensing analysis has revealed that there are several landforms in the high-latitude regions in both hemispheres that suggest the presence of liquid brine during the summer. This suggests the possibility of an active groundwater cycle originating from subglacial lakes beneath polar ice-caps.
In Topic (1), we examined the delta topography on the Martian surface and its relationship with ancient sea-level changes using the flume-tank experimental at Nagasaki University. Then, we examined formation ages of each delta topography by the crater counting method. As a result, we found that the deltas formed by sea-level fall are dated to be at about 3.6~3.5 billion years ago, while the deltas formed by water-level rise in the crater are dated to be at about 3.4~3.2 billion years ago. Based on this evidence, we propose the hypothesis that the northern lowland oceans that spread on ancient Mars disappeared by 3.5~3.4Ga and were replaced by an environment with localized lakes.
In Topic (2), we are attempting to estimate the distribution of subsurface ice in the mid-latitude of Mars as a preceding exploration of the Mars Ice Mapper (MIM) project, an international Mars exploration program planned for the early 2030s. In this study, we focused on periglacial landforms (thermal contraction polygons and pingos) formed by the presence of subsurface ice that develop in the permafrost regions of the Earth. For estimating the subsurface ice distribution of mid-latitude Mars, we chose Mongolia, where the boundary between the permafrost and desert belts is located, as an important terrestrial analog site. By applying our findings of the relationship between the shape of periglacial landforms and the permafrost distribution in Mongolia, we were able to estimate the subsurface ice distribution in the mid-latitude of Mars.
In Topic (3), we are attempting to verify the possibility of the existence of liquid brine in the high-latitude regions of Mars. Remote-sensing analysis has revealed that there are several landforms in the high-latitude regions in both hemispheres that suggest the presence of liquid brine during the summer. This suggests the possibility of an active groundwater cycle originating from subglacial lakes beneath polar ice-caps.