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Formation of gullies on Mars by debris flows triggered by CO_2 sublimation

Pilorget, C. and Forget, F. (2016) Formation of gullies on Mars by debris flows triggered by CO_2 sublimation. Nature Geoscience, 9 (1). pp. 65-69. ISSN 1752-0894. doi:10.1038/ngeo2619.

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Martian gully landforms resemble terrestrial debris flows formed by the action of liquid water and have thus been interpreted as evidence for potential habitable environments on Mars within the past few millennia. However, ongoing gully formation has been detected under surface conditions much too cold for liquid water, but at times in the martian year when a thin layer of seasonal CO_2 frost is present and defrosting above the regolith. These observations suggest that the CO_2 condensation–sublimation cycle could play a role in gully formation. Here we use a thermo-physical numerical model of the martian regolith underlying a CO_2 ice layer and atmosphere to show that the pores beneath the ice layer can be filled with CO_2 ice and subjected to extreme pressure variations during the defrosting season. The subsequent gas fluxes can destabilize the regolith material and induce gas-lubricated debris flows with geomorphic characteristics similar to martian gullies. Moreover, we find that subsurface CO_2 ice condensation, sublimation and pressurization occurs at conditions found at latitudes and slope orientations where gullies are observed. We conclude that martian gullies can result from geologic dry ice processes that have no terrestrial analogues and do not require liquid water. Such dry ice processes may have helped shape the evolution of landforms elsewhere on the martian surface.

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Alternate Title:Formation of gullies on Mars by debris flows triggered by CO2 sublimation
Additional Information:© 2016 Macmillan Publishers Limited. Received 14 August 2015. Accepted 16 November 2015. Published online 21 December 2015. We would like to thank A. Mangeney, M. Vincendon, P.-Y. Meslin and L. Kerber for fruitful discussions about this work. We are also grateful to our colleagues at Caltech, IAS and LMD for inspiration and advice. C.P. acknowledges partial support from NNX14AG54G and CNES. Finally, we thank C. Dundas for constructive comments. Contributions: C.P. and F.F. developed the model and wrote the manuscript. C.P. run the simulations and performed the analyses. The authors declare no competing financial interests.
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Centre National d'Études Spatiales (CNES)UNSPECIFIED
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Record Number:CaltechAUTHORS:20160115-103717353
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Official Citation:Formation of gullies on Mars by debris flows triggered by CO2 sublimation C. Pilorget & F. Forget Nature Geoscience 9, 65–69 (2016) doi:10.1038/ngeo2619
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63704
Deposited By: George Porter
Deposited On:19 Jan 2016 21:21
Last Modified:10 Nov 2021 23:20

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