Permafrost molards as an analogue for ejecta-ice interactions at Hale Crater, Mars

• Published in: Icarus
• Main Authors: Morino, Costanza, Conway, Susan, Philippe, Meven, Peignaux, Coralie, Svennevig, Kristian, Lucas, Antoine, Noblet, Axel, Roberti, Gioachino, Butcher, Frances, Collins-May, Jake
• Other Authors: Environnements, Dynamiques et Territoires de Montagne (EDYTEM), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géosciences UMR_C 6112 (LPG), Le Mans Université (UM)-Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST), Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ), Geological Survey of Denmark and Greenland (GEUS), Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), University of Sheffield Sheffield, Newcastle University Newcastle, ANR-19-CE01-0010,Permolards,Les molards, marqueurs de l'évolution de la dégradation du pergélisol de montagne(2019)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology; Canada; Greenland; Hale; Main Crater; Paatuut; Ice; permafrost
• Online Access: https://hal.science/hal-03866697; https://hal.science/hal-03866697/document; https://hal.science/hal-03866697/file/1-s2.0-S0019103522004559-main.pdf; https://doi.org/10.1016/j.icarus.2022.115363

International audience When the Hale impact crater penetrated the martian cryosphere 1Ga, landforms indicating post-impact volatile mobilisation were generated. We have found landforms in the ejecta blanket of Hale Crater similar to ‘permafrost molards’ found in periglacial environments on Earth, and probably related to the past or present presence of volatiles at/near the surface. Permafrost molards are conical mounds of debris associated with landslide deposits, resulting from the degradation of blocks of ice-rich material mobilised by a landslide in periglacial terrains. Here we analyse the spatial and topographic distribution of conical mounds around the Hale crater at regional and local scales, and compare them to those of molards on the deposits of the Mount Meager debris avalanche in Canada. Hale Crater's conical mounds are located at the distal boundary of the thickest ejecta blanket, which is the closest to the main crater. We observe a similar spatial arrangement of molards along the distal parts of the terminal lobe of the Mount Meager debris avalanche. We then compare the morphology and morphometrics of the conical mounds on Hale Crater to those of terrestrial molards on the Paatuut and Niiortuut rock avalanches in western Greenland. We find that morphology and setting of conical mounds within Hale Crater ejecta are consistent with the formation pathway of molards on Earth. We infer that they originated from blocks of ice-cemented regolith that were produced by the Hale-crater-forming impact, transported by the ejecta flows, and finally degraded to cones of debris (molards) on loss of the interstitial ice. The similarities in distribution between the ejecta flows of Hale and Mount Meager debris avalanche on Earth suggest that the mounds resulted from the rheological separation of the ejecta flows, with a relatively fluid-poor phase that allowed the volatile-rich blocks to survive transport. This supports the prevailing hypothesis that the Hale impact event penetrated the martian cryosphere, ...