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The formation of gullies on Mars today

By
Colin M. Dundas
Colin M. Dundas
Astrogeology Science Center, United States Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001, USA
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Alfred S. McEwen
Alfred S. McEwen
Lunar and Planetary Laboratory, The University of Arizona, 1629 E University Blvd, Tucson, AZ 85721, USA
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Serina Diniega
Serina Diniega
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
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Candice J. Hansen
Candice J. Hansen
Planetary Science Institute, 1700 E. Fort Lowell, Tucson, AZ 85719, USA
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Shane Byrne
Shane Byrne
Lunar and Planetary Laboratory, The University of Arizona, 1629 E University Blvd, Tucson, AZ 85721, USA
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Jim N. McElwaine
Jim N. McElwaine
Planetary Science Institute, 1700 E. Fort Lowell, Tucson, AZ 85719, USA
Department of Earth Sciences, Durham University, Elvet Hill, Durham DH1 3LE, UK
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Published:
January 01, 2019

Abstract

A decade of high-resolution monitoring has revealed extensive activity in fresh Martian gullies. Flows within the gullies are diverse: they can be relatively light, neutral or dark, colourful or bland, and range from superficial deposits to 10 m-scale topographic changes. We observed erosion and transport of material within gullies, new terraces, freshly eroded channel segments, migrating sinuous curves, channel abandonment, and lobate deposits. We also observed early stages of gully initiation, demonstrating that these processes are not merely modifying pre-existing landforms. The timing of activity closely correlates with the presence of seasonal CO2 frost, so the current changes must be part of ongoing gully formation that is driven largely by its presence. We suggest that the cumulative effect of many flows erodes alcoves and channels, and builds lobate aprons, with no involvement of liquid water. Instead, flows may be fluidized by sublimation of entrained CO2 ice or other mechanisms. The frequent activity is likely to have erased any features dating from high-obliquity periods, so fresh gully geomorphology at middle and high latitudes is not evidence for past liquid water. CO2 ice-driven processes may have been important throughout Martian geological history and their deposits could exist in the rock record, perhaps resembling debris-flow sediments.

Supplementary material: Figures, animations and a summary table describing details of known gully activity are available at https://doi.org/10.6084/m9.figshare.c.3936886

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Contents

Martian Gullies and their Earth Analogues
CONTAINS OPEN ACCESS

S. J. Conway
S. J. Conway
Centre National de la Recherche Scientifique, France
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J. L. Carrivick
J. L. Carrivick
University of Leeds, UK
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P. A. Carling
P. A. Carling
University of Southampton, UK
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T. de Haas
T. de Haas
University of Utrecht, The Netherlands
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T.N. Harrison
T.N. Harrison
Arizona State University, USA
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Geological Society of London
Volume
467
ISBN electronic:
9781786203625
Publication date:
January 01, 2019

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