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The dynamics of CO2-driven granular flows in gullies on Mars
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  • Lonneke Roelofs,
  • Susan J Conway,
  • Bas van Dam,
  • Arjan van Eijk,
  • Jonathan peter Merrison,
  • J. J. Iversen,
  • Matthew E. Sylvest,
  • Manish R Patel,
  • Henk Markies,
  • Marcel van Maarseveen,
  • Jim McElwaine,
  • Maarten G. Kleinhans,
  • Tjalling de Haas
Lonneke Roelofs
Utrecht University

Corresponding Author:l.roelofs@uu.nl

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Susan J Conway
University of Nantes
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Bas van Dam
Universiteit Utrecht
Arjan van Eijk
Universiteit Utrecht, Universiteit Utrecht
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Jonathan peter Merrison
Aarhus University
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J. J. Iversen
University of Aarhus
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Matthew E. Sylvest
The Open University
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Manish R Patel
The Open University
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Henk Markies
Universiteit Utrecht
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Marcel van Maarseveen
Universiteit Utrecht
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Jim McElwaine
Durham University
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Maarten G. Kleinhans
Universiteit Utrecht
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Tjalling de Haas
Universiteit Utrecht
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Abstract

Martian gullies are landforms consisting of an erosional alcove, a channel, and a depositional apron. A significant proportion of Martian gullies at the mid-latitudes is active today. The seasonal sublimation of CO2 ice has been suggested as a driver behind present-day gully activity. However, due to a lack of in-situ observations, the actual processes causing the observed changes remain unresolved. Here, we present results from flume experiments in environmental chambers in which we created CO2-driven granular flows under Martian atmospheric conditions. Our experiments show that under Martian atmospheric pressure, large amounts of granular material can be fluidized by the sublimation of small quantities of CO2 ice in the granular mixture (only 0.5% of the volume fraction of the flow) under slope angles as low as 10°. Dimensionless scaling of the CO2-driven granular flows shows that they are dynamically similar to terrestrial two-phase granular flows, i.e. debris flows and pyroclastic flows. The similarity in flow dynamics explains the similarity in deposit morphology with levees and lobes, supporting the hypothesis that CO2-driven granular flows on Mars are not merely modifying older landforms, but they are actively forming them. This has far-reaching implications for the processes thought to have formed these gullies over time. For other planetary bodies in our solar system, our experimental results suggest that the existence of gully-like landforms is not necessarily evidence for flowing liquids but that they could also be formed or modified by sublimation-driven flow processes.