Abstract
Long-runout landslides with transport distances of >50 km are ubiquitous in Valles Marineris (VM), yet the transport mechanisms remain poorly understood. Four decades of studies reveal significant variation in landslide morphology and emplacement age, but how these variations are related to landslide transport mechanisms is not clear. In this study, we address this question by conducting systematic geological mapping and compositional analysis of VM long-runout landslides using high-resolution Mars Reconnaissance Orbiter imagery and spectral data. Our work shows that: (1) a two-zone morphological division (i.e., an inner zone characterized by rotated blocks and an outer zone expressed by a thin sheet with a nearly flat surface) characterizes all major VM landslides; (2) landslide mobility is broadly dependent on landslide mass; and (3) the maximum width of the outer zone and its transport distance are inversely related to the basal friction that was estimated from the surface slope angle of the outer zone. Our comprehensive Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) compositional analysis indicates that hydrated silicates are common in landslide outer zones and nearby trough-floor deposits. Furthermore, outer zones containing hydrated minerals are sometimes associated with longer runout and increased lateral spreading compared to those without detectable hydrated minerals. Finally, with one exception we find that hydrated minerals are absent in the inner zones of the investigated VM landslides. These results as whole suggest that hydrated minerals may have contributed to the magnitude of lateral spreading and long-distance forward transport of major VM landslides.
Highlights
Enigmatic long-runout (>50 km) landslides have sculpted the morphology of Valles Marineris (VM) on Mars over the past 3.5 billion years (Blasius et al, 1977; Lucchitta, 1979; McEwen, 1989; Witbeck et al, 1991; Quantin et al, 2004a, 2004b; Crosta et al, 2018) (Fig. 1)
Our morphometric analyses of VM landslides indicate that the outer-zone spreading width and landslide mass inferred from the width of the breakaway zone increase with runout distance, and the lateral taper angle of the outer-zone lobes measured in the direction perpendicular to that of landslide transport decreases with increasing outer-zone runout distance
Quantitative morphologic investigation of landslides in VM reveals a characteristic two-zone morphology that persists despite emplacement age, subclass, and location
Summary
Enigmatic long-runout (>50 km) landslides have sculpted the morphology of Valles Marineris (VM) on Mars over the past 3.5 billion years (Blasius et al, 1977; Lucchitta, 1979; McEwen, 1989; Witbeck et al, 1991; Quantin et al, 2004a, 2004b; Crosta et al, 2018) (Fig. 1). The opening of the VM troughs may have started in the Late Noachian (e.g., Dohm et al, 2009) and lasted as late as the Late Amazonian (Blasius et al, 1977; Schultz, 1998; Witbeck et al, 1991; Yin, 2012b) Due to their exceptional exposure and nearly complete preservation of surface morphology, VM landslides have been intensely studied since they were first revealed by Mariner 9 and Viking images (e.g., Lucchitta, 1978, 1979, 1987; McEwen, 1989; Schultz, 2002; Harrison and Grimm, 2003; Quantin et al, 2004a, 2004b; Soukhovitskaya and Manga, 2006; Lajeunesse et al, 2006; Bigot-Cormier and Montgomery, 2007; Lucas and Mangeney, 2007; Lucas, 2011; De Blasio, 2011; Brunetti et al, 2014; Watkins et al, 2015). Subsequent studies based on higher-resolution images indicate a wide (http://creativecommons.org/licenses/by/4.0/)
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