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Communication Dans Un Congrès Année : 2020

Initiation and flow conditions of contemporary flows in Martian gullies

Tjalling de Haas
Brian Mcardell
  • Fonction : Auteur
Jim Mcelwaine
  • Fonction : Auteur
Maarten Kleinhans
  • Fonction : Auteur
Francesco Salese
  • Fonction : Auteur
Peter Grindrod
  • Fonction : Auteur

Résumé

<p>Understanding the initial and flow conditions of contemporary flows in Martian gullies, generally believed to be triggered and fluidized by CO<sub>2</sub> 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&#8211;1.5 m and initial release volumes of 100&#8211;200 m<sup>3</sup>. Entrainment leads to final flow volumes that are 2.5&#8211;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&#8211;4 m s<sup>-1</sup> to ~1 m s<sup>-1</sup> from release area to flow terminus, while flow depths generally decrease from 0.5&#8211;1 m to 0.1&#8211;0.2 m. The mean cross-channel erosion depth and deposition thicknesses are _0.1&#8211;0.3 m. Back-calculated dry-Coulomb friction ranges from 0.1 to 0.25 and viscous turbulent friction between 100&#8211;200 m s<sup>-2</sup>, 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 CO<sub>2</sub> sublimation we are able to show that under Martian atmospheric conditions very small volumetric fractions of CO<sub>2</sub> of ~1% within mass flows may indeed yield sufficiently large gas fluxes to cause fluidization and enhance flow mobility.</p>

Dates et versions

hal-03091555 , version 1 (31-12-2020)

Identifiants

Citer

Tjalling de Haas, Brian Mcardell, Susan J. Conway, Jim Mcelwaine, Maarten Kleinhans, et al.. Initiation and flow conditions of contemporary flows in Martian gullies. 22nd EGU General Assembly, May 2020, held online, Unknown Region. ⟨10.5194/egusphere-egu2020-7802⟩. ⟨hal-03091555⟩
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