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Geologic history of the polar regions of Mars based on Mars Global surveyor data. II. Amazonian period

Icarus

By:
and
DOI: 10.1006/icar.2001.6676

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Abstract

Based on Mars Orbiter Laser Altimeter (MOLA) and Mars Orbiter Camera (MOC) observations of Amazonian polar layered deposits' (PLD) morphology, composition, and thickness, we conclude that the PLDs are composed of porous unconsolidated layers that have not experienced significant basal melting or other glacial-type processes. Morphologic features and associations within the PLD chasmata, including preserved craters and sinuous ridges, indicate that the dominant process of chasmata formation is wind scouring. Our detailed analysis of south polar spiral-trough topography, in conjunction with the identification of similar layered stratigraphy within north polar spiral troughs, suggests that trough migration due to preferential ablation of Sun-facing slopes cannot be demonstrated. Within the layered sequences, we have not identified widespread unconformities, discontinuities, or pinch-outs that would indicate an accublation origin of the PLDs. We therefore postulate that the well-defined PLDs at both poles eventually reached and maintained their present form following deposition without extensive deformation or redeposition. Large, cuspate ridges in the Ultimi lobe of Planum Australe appear to be layered and may be unusual erosional remnants of a once thicker PLD in this area. Beneath the north polar layered deposits in Planum Boreum, we have identified a platform of older, highly degraded polar deposits as much as a kilometer thick that may have once covered an area larger than Planum Boreum. ?? 2001 Elsevier Science.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Geologic history of the polar regions of Mars based on Mars Global surveyor data. II. Amazonian period
Series title:
Icarus
DOI:
10.1006/icar.2001.6676
Volume
154
Issue:
1
Year Published:
2001
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Icarus
First page:
22
Last page:
39