Gullies and landslides on the Moon: Evidence for dry‐granular flows

Abstract

[1] High-resolution images from Chandrayaan-1 Terrain Mapping Camera and Lunar Reconnaissance Orbiter Camera reveal landslides and gully formation on the interior wall of a 7 km-diameter simple crater emplaced in Schrödinger basin on the farside of the Moon. These features occur on the steep upper crater wall, where the slope is ~35. The gullies show a typical alcove-channel-fan morphology. Some gullies incise bedrock, where impact-related faults are present. Slope failure along the concentric faults also led to formation of landslides. Dark slope streaks are abundant at the bright gully regions, especially near the fan and channel deposits. Spectral characteristics inferred from data obtained by Hyperspectral Imager and Moon Mineralogy Mapper on board Chandrayaan-1 show that the gullies and landslides are characterized by high optical immaturity and devoid of prominent spectral absorption features related to water or hydroxyl molecules, suggesting youthful dry-granular flows. Mass movements on the crater wall led to the formation of arcuate ridges and ponding of fine-grained sediments on the crater floor. Runout flows from small impact craters on the slopes indicate that impact-induced seismic shaking was responsible for the downslope mass movements. Crater size-frequency distributions suggest a minimum age of 18-2 Ma for the gullies and 2 Ma for the landslides, while age of the host crater ejecta was inferred to be about 175 Ma. The gullies and landslides also occur on the interior wall of other impact craters elsewhere on the Moon and probably formed by similar processes.

Geologic map of the northern hemisphere of Vesta based on Dawn Framing Camera (FC) images

“…10). However, smooth-surfaced ponds of fine debris are observed on the Moon with a similar appearance (e.g., Kumar et al, 2013). The occurrences of unit s in Licinia crater shows morphologies that are also very similar to impact melt deposits on the lunar surface (e.g., Plescia and Cintala, 2012;Schultz, 1976).…”

“…7a, reminiscent of a fine-grained avalanche. Note also that albedo streaks might not only result from compositional variations, but could be due to removal of a thin layer of fine-grained material (e.g., Schorghofer and King, 2011;Kumar et al, 2013).…”

Volcanism on farside of the Moon: New evidence from Antoniadi in South Pole Aitken basin

“…There are eight simple impact craters (13 km, 7.7 km, 6.6 km, 3.6 km, 2.8 km, 1.9 km, 1.8 km, and 1.5 km diameter) emplaced on the basin; these were mapped as young crater material (area 1.1 Â 10 3 km 2 ), which includes the ejecta material (area 0.8 Â 10 3 km 2 ) of the largest young crater (13 km-sized crater). There are gullies and landslides on the walls of young craters and the basin wall (e.g., Kumar et al, 2010Kumar et al, , 2013. The structural units are faults and grabens.…”

The unique geomorphology and physical properties of the Vestalia Terra plateau

“…However, similar mass-wasting lobes and gully-like features have also been successfully reproduced in models of dry granular flow on both the Moon (e.g. Bart, 2007;Senthil Kumar et al, 2013) and Mars (e.g. Shinbrot et al, 2004).…”

“…There is a bright layer evident in the sharp western wall, from which gullylike features consistent with dry granular flow (e.g. Shinbrot et al, 2004;Bart, 2007;Senthil Kumar et al, 2013;Scully et al, 2014;Krohn et al, 2014) seem to begin. However, upon closer examination these 'gullies' are the edges of mass-wasting lobes flowing down the crater wall (Fig.…”