
North polar region of Mars: Topography of circumpolar deposits from Mars Orbiter Laser Altimeter (MOLA) data and evidence for asymmetric retreat of the polar cap
Author(s) -
Fishbaugh Kathryn E.,
Head James W.
Publication year - 2000
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/1999je001230
Subject(s) - geology , mars exploration program , impact crater , fluvial , geomorphology , orbiter , geochemistry , sedimentary rock , astrobiology , structural basin , physics , aerospace engineering , engineering
We have used high‐resolution Mars Orbiter Laser Altimeter (MOLA) data to analyze the topography, morphology, stratigraphy, and geologic history of the Martian north circumpolar deposits. The present polar deposits are offset about toward 0°W from the rotational pole. An arc of irregular topography, concentric to Olympia Planitia and the cap, consists of polar material remnants, depressions which we interpret to be kettles, frost‐covered and residual ice‐filled craters, and frost patches. Olympia Planitia, originally thought to be a flat, sand‐covered plain, is characterized by a convex‐upward topography, contiguous with the polar cap. We interpret Olympia Planitia to represent a now dune‐covered extension of the polar materials. Together, Olympia Planitia and the outlying deposits delineate a former extent of the polar cap. Topographic data have clarified relationships among the circumpolar deposits. Contributors to these deposits include local volcanics, fluvial and aqueous sediments (from outflow channels and a possible standing body of water), pyroclastic ash, sublimation lag from the Olympia Lobe, and eolian‐reworked materials. Significant events in the history of the region include (1) formation of the northern lowlands; (2) emplacement of volcanic plains, fluvial and aqueous sedimentation, and subsequent desiccation, forming polygonal patterns which in part underlie the present polar layered deposits; (3) formation of the polar cap, composed primarily of layered deposits; (4) asymmetric retreat of the Olympia Lobe, resulting in sublimation lag deposits, polar remnants, and kettles; and (5) continued collection and reworking of sediments by eolian processes. The cause of the asymmetrical retreat of the Olympia Lobe is unknown.