11:30 〜 11:45
[PPS06-09] Discovery of Martian Brain Terraine-like Geomorphology from Mongolia
キーワード：Mars, Brain Terrain, Ice deposit, Mongolia, Analog study, Periglacial
To survive (humans and organisms) on Mars water is a necessary component. Future human explorations are planned on the mid-latitudes where water ice is only stable in the subsurface. For that purpose, patterned grounds (Korteniemi and Kreslavsky, 2013) formed by freeze-thaw mechanisms of subsurface ice (Mangold et al., 2004) in the Martian mid-latitudes are current targets to support future exploration (MDT report 2022). Among others, Brain Terrain (BT) is the most commonly occurring patterned ground (Levy et al. 2009) and subsequent RADAR data has verified the presence of ice beneath (Levy et al., 2014). However, the ice's depth and the volume of the ice reserve are not known, therefore, the study of their terrestrial analogs is essential. Unfortunately, the periglacial BTs have never been reported on Earth; because of their bare minimum trough depth which makes it hard to find from satellite images, and their occurrences in flat terrains keep them unrecognizable even on the grounds.
We report, for the first time, the identification of Brain Terrain (BT) within the southern permafrost regions of north and central Mongolia. These BTs differ morphologically—ridge length, trough width, and depth—depending on the depth of the underlying permafrost layer. A trench excavation provided a sectional view indicating seasonal freeze-thaw cycle-derived cracks that become filled with ice wedges. Over time, the space between these cracks widens to form troughs, with continued seasonal sedimentation from the surrounding area resulting in distinct lamination and the deposition of fine-grained sediments within the troughs.
We observe that the orientation of BTs can be influenced by the pre-existing topography. Furthermore, the seasonal melting of ice just beneath the trough sediments maintains a moist environment, likely leading to a more organic-rich (and visibly darker) soil compared to adjacent areas. This is reflected on the surface by a higher density of vegetation, such as grass, growing over these troughs. This significant finding sheds light on the intricate connections between surface topography, subsurface ice distribution, the preservation of astrobiological materials, and their formation process.
We report, for the first time, the identification of Brain Terrain (BT) within the southern permafrost regions of north and central Mongolia. These BTs differ morphologically—ridge length, trough width, and depth—depending on the depth of the underlying permafrost layer. A trench excavation provided a sectional view indicating seasonal freeze-thaw cycle-derived cracks that become filled with ice wedges. Over time, the space between these cracks widens to form troughs, with continued seasonal sedimentation from the surrounding area resulting in distinct lamination and the deposition of fine-grained sediments within the troughs.
We observe that the orientation of BTs can be influenced by the pre-existing topography. Furthermore, the seasonal melting of ice just beneath the trough sediments maintains a moist environment, likely leading to a more organic-rich (and visibly darker) soil compared to adjacent areas. This is reflected on the surface by a higher density of vegetation, such as grass, growing over these troughs. This significant finding sheds light on the intricate connections between surface topography, subsurface ice distribution, the preservation of astrobiological materials, and their formation process.