Overlapping Lobate Deposits in Martian Gullies

Post contributed by Rishitosh K. Sinha, Planetary Sciences Division, Physical Research Laboratory, India.

Gullies are found on steep slopes on the surface of Mars and appear as a linear-to-sinuous channel linking an alcove at the top to a fan at the bottom. The most interesting interpretation of the past two decades has been that the Martian gullies were carved by the flow of liquid water as discovered from the high-resolution images returned by the Mars Orbiter Camera (MOC) onboard “Mars Global Surveyor (MGS)” in 2000 (Malin and Edgett, 2000). Subsequent observations using MOC and the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) images revealed that Martian gullies are active today and that sublimation of seasonal carbon dioxide frost – not liquid water – could have played an important role in their formation. In our recent work using HiRISE images we reported global distribution of overlapping lobate deposits in gullies (Image 1) showing that a debris-flow like process may be responsible for gully formation (Sinha et al., 2020).

Image 1: Top: 3D view of gullies on the pole-facing wall of ~8 km diameter Los crater (35.08˚ S, 76.22˚ W) on Mars. HiRISE image ESP_020774_1445 (0.25 m/pixel) is draped over 1 m/pix HiRISE elevation model. The depth of crater floor from the crater rim is ~1 km in elevation and the image spans ~4 km from left to right. The box shows the location of bottom panel. Bottom: Image shows the gully fan surface within Los crater with overlapping lobate deposits, including convex-up and tongue shaped terminal lobes with lateral levees. HiRISE image credits: NASA/JPL/University of Arizona.

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Very recent debris flow activity on Mars

Post contributed by Dr Andreas Johnsson, Department of Earth Sciences, University of Gothenburg, Sweden.

The question whether Martian gullies formed by fluvial processes or by dry mass wasting have been a source of heated debate ever since their discovery (Malin and Edgett, 2000). Intense research within the last decade however points to a fluvial origin for a majority of gully landforms on Mars.

Image 1. A) Overview of the pole-facing interior crater wall (PSP_006837_1345). B) Clearly defined paired levee deposits (white arrows). C) Multiple overlapping lobate deposits (white arrows). D) Gully fan dominated by debris flows (white arrows). E) Well defined medial deposit (debris plug) (white arrow).  Image credit: NASA/JPL/UofA for HiRISE.

Image 1. A) Overview of the pole-facing interior crater wall (PSP_006837_1345). B) Clearly defined paired levee deposits (white arrows). C) Multiple overlapping lobate deposits (white arrows). D) Gully fan dominated by debris flows (white arrows). E) Well defined medial deposit (debris plug) (white arrow). Image credit: NASA/JPL/UofA for HiRISE.

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