EGU2020-7802
https://doi.org/10.5194/egusphere-egu2020-7802
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Initiation and flow conditions of contemporary flows in Martian gullies

Tjalling de Haas1, Brian McArdell2, Susan Conway3, Jim McElwaine4,5, Maarten Kleinhans1, Francesco Salese1, and Peter Grindrod6
Tjalling de Haas et al.
  • 1Universiteit Utrecht, Faculty of Geosciences, Physical Geography, Utrecht, Netherlands (t.dehaas@uu.nl)
  • 2Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
  • 3Laboratoire de Planétologie et Géodynamique, Université de Nantes, Nantes, France
  • 4Department of Earth Sciences, Durham University, Durham, UK
  • 5Planetary Science Institute, Tucson, USA
  • 6Department of Earth Sciences, Natural History Museum, London, UK.

Understanding the initial and flow conditions of contemporary flows in Martian gullies, generally believed to be triggered and fluidized by CO2 sublimation, is crucial for deciphering climate conditions needed to trigger and sustain them. We employ the RAMMS (RApid Mass Movement Simulation) debris flow and avalanche model to back-calculate initial and flow conditions of recent flows in three gullies in Hale crater. We infer minimum release depths of 1.0–1.5 m and initial release volumes of 100–200 m3. Entrainment leads to final flow volumes that are 2.5–5.5 times larger than initially released, and entrainment is found necessary to match the observed flow deposits. Simulated mean cross-channel flow velocities decrease from 3–4 m s-1 to ~1 m s-1 from release area to flow terminus, while flow depths generally decrease from 0.5–1 m to 0.1–0.2 m. The mean cross-channel erosion depth and deposition thicknesses are _0.1–0.3 m. Back-calculated dry-Coulomb friction ranges from 0.1 to 0.25 and viscous turbulent friction between 100–200 m s-2, which are values similar to those of granular debris flows on Earth. These results suggest that recent flows in gullies are fluidized to a similar degree as are granular debris flows on Earth. Using a novel model for mass-flow fluidization by CO2 sublimation we are able to show that under Martian atmospheric conditions very small volumetric fractions of CO2 of ~1% within mass flows may indeed yield sufficiently large gas fluxes to cause fluidization and enhance flow mobility.

How to cite: de Haas, T., McArdell, B., Conway, S., McElwaine, J., Kleinhans, M., Salese, F., and Grindrod, P.: Initiation and flow conditions of contemporary flows in Martian gullies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7802, https://doi.org/10.5194/egusphere-egu2020-7802, 2020.

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