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Glacial Origin of Landform Assemblages in Western Jezero Crater, Mars
  • An Yin
An Yin
University of California Los Angeles

Corresponding Author:ayin54@gmail.com

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HiRISE-based mapping reveals five landform assemblages in western Jezero crater, each defined by a landform association interpretable using Earth-based landsystem models and well-understood Earth analogues. 1) The northwestern assemblage hosts boulder hills rimmed by lobate ridges, mounds and mesas on a valley floor, and valley-bounding ridges superposed by striations (= parallel boulder-bearing ridges and grooves). 2) A trough zone hosts variously shaped depressions, intra-trough islands, linear and curvilinear boulder ridges, and highland strips topped by striated surfaces and rimmed by boulder-bearing ridges. 3) The steep-sided fan-shaped plateau (“western Jezero delta”) hosts mesas, highland-rim boulder ridges, depressions, linear and curvilinear ridges, and a plain superposed by radially trending striations. 4) The crater-margin assemblage hosts a steep-sided ridged and pitted hummocky terrain, a terrace-like capping surface, and mounds surrounded by radially trending boulder ridges. 5) The crater-floor assemblage hosts a polished and striated terrain that displays fold-like and streamlined ridges, hummocky landforms dominated by quasi-circular depressions with raised rims, mesas exposing fold-thrust strata, flat-topped steep-sided ridges with U-shaped map traces, polygonal-grooved plains, and unconsolidated boulder mounds and ridges. Although any aforementioned landform unit could be explained by multiple formative mechanisms, the spatiotemporal relationships mapped in this study within and among the assemblages place stringent constraints for any self-consistent interpretation. A model capable of explaining the mapping results involves northeast-flowing glaciation, ice-sheet collapse with ice-fracture patterns controlling the formation of polygonal grooves via crevasse filling and ice pressing, and minor aeolian modification. In the model, the plateau and crater-margin assemblages were formed by ice-walled subglacial deposition, the trough zone by subglacial flooding, the northwestern and basin-floor assemblages by glacial deformation and deposition, circular depressions with raised rims by melt out and down pressing of spherical dead-ice blocks (i.e., thermal karsts and kettle holes), mesas by kame formation, and striations by glacial fluting.