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Terrestrial Recurring Slope Lineae in Mongolia : Its Formation Mechanism and Implications for Mars
| Content Provider | Semantic Scholar |
|---|---|
| Author | Nakamura, Mototaka Sekine, Yoshitsugu Fukushi, Keisuke Hasebe, N. Davaadorj, D. Takahashi, Yukihiro Hasegawa, Hiroshi Ogura, Takuro Morida, K. Tuvshin, G. |
| Copyright Year | 2019 |
| Abstract | Introduction: Recurring Slope Lineae (RSL) are dark, narrow features that appear and lengthen on steep (~30°) slopes in warm seasons and fade in cold seasons of Mars [1,2,3]. Several processes have been proposed for the formation mechanism of RSL, including liquid brine flows triggered by melting of subsurface briny ice (the wet flow hypothesis) [4], and granular flows on slopes (the dry flow hypothesis) [5]. However, the formation mechanism of RSL is still in debate because of a difficulty of geological survey for Martian RSL. Here, we report terrestrial Recurring Slope Lineae (terrestrial RSL) in cold, arid areas of central Mongolia. In our previous study [6], we found the narrow dark streak features in Mongolia. In the present study, we report a time evolution of these features over years to confirm its recurrence (appearance and dissipation). We also conduct geological surveys for the terrestrial RSL several times in different seasons to investigate its formation mechanism. Based on the geological survey, we discuss the required water mass flux and possible source of water to form Martian RSL when the formation mechanism of the terrestrial RSL can be applied to Martian ones. Terrestrial recurring slope lineae in Mongolia: In the previous study, we searched RSL-like dark, narrow features over Earth’s surface using satellite images [6]. We found terrestrial RSL only in cold and arid, southern part of Khangai Mountains in central Mongolia (Fig. 1) [6]. In this area where RSL are found, discontinuous permafrost and underground ice melt seasonally [7]. The terrestrial RSL favor equator-facing downslopes from bedrock outcrops. The width and length of terrestrial RSL are 0.5–5 m and 100–150 m, respectively (Fig. 1), comparable to those of Martian RSL [1,2,3], although the slope angles of the terrestrial analogues (~10–12o) are shallower than those of typical Martian RSL (~30o). The terrestrial RSL also initiate from fractures of the basement rocks (Fig. 1), which are often seen in Martian RSL. Based on the satellite images taken in different seasons and visual images taken by an unmanned aerial vehicle in our geological surveys (see below), the present study finds that terrestrial RSL are recurring over years (Fig. 1). Similar to Martian RSL, terrestrial RSL also appear on slopes in warm seasons (e.g., August and early September: Fig. 1a and 1d) and fade in cold and dry seasons (e.g., late September and December: Fig. 1c and 1e). Dissipation of the RSL would not be caused by snow coverage on the surface. Despite small snow patches are seen in the satellite image of December 2018, snow uncovers entirely the slope, where the RSL fade (Fig. 1e). The observed similarities in morphology and seasonal activity strongly suggest that the terrestrial RSL in Mongolia are promising analogues of Martian RSL. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www.hou.usra.edu/meetings/ninthmars2019/pdf/6172.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
