[M-IS17] Aqua planetology

[MIS17-10] Relationship between water equivalent hydrogen abundances and slope streaks distribution in the Medusae Fossae Formation

*Shun Mihira^1,2, Trishit Ruj², Tomohiro Usui² (1.The university of Tokyo, 2.Institute of Space and Astronautical Science, JAXA)

Keywords:Mars, Slope streaks

Slope streaks are dark linear features on the slopes of Mars which appear at a certain time and gradually fade away over a period of 10 years (Sullivan et al., 2001). In general, slope streaks are frequently observed in the equatorial to subequatorial dusty regolith regions with low thermal inertia (Kreslavsky & Head, 2009). Recent studies have shown that the global distribution of slope streaks is consistent with the regions with high abundances of Gamma-Ray Spectrometer-derived water-equivalent hydrogen on Mars (Bhardwaj et al. 2017). Even though the formation mechanism of slope streaks is still unclear, both wetting mechanisms, such as subsurface ice melting, and drying mechanisms, including the movement of the granules, have been proposed (Ferris et al. 2002; Bulmer et al. 2008; Bhardwaj et al. 2018). Bhardwaj et al. (2017) suggest that the formation of slope streaks is due to the interaction of regolith with atmospheric water on a daily scale. However, scientists (refs) also have argued that the morphological and terrain variations of slope streaks cannot explain such wetting mechanism alone. Therefore, it is supposed that a hypothesis that takes into account both dry and wet processes can provide a more comprehensive explanation of all morphological diversity of the observed slope streaks (Bhardwaj et al. 2018).
The Medusae Fossae Formation (MFF) has geologic features that indicate wind erosion of low-density material near the equator (Ojha et al., 2018) and is one of the regions where a large number of slope streaks have been observed (Ferris et al. 2002). It is also one of the regions with high-water equivalent hydrogen abundances (Bhardwaj et al. 2017). Since some hypotheses on the formation process of slope streaks are based on the melting of subsurface ice (Ferris et al. 2002), the MFF is an ideal place to study the formation process of slope streaks due to the number of slope streaks, the amount of hydrogen, and the possibility of the existence of subsurface ice.
We mapped the distribution of slope streaks in and around the MFF in detail. As a result, it was found that the distribution of slope streaks was consistent with that of water equivalent hydrogen content in the MFF. We believe that the formation mechanism of slope streaks is related to the enrichment of hydrogen concentration.