Modeling the Formation of Lobate Debris Aprons on Mars by Creep of Ice-rich Permafrost

Details Modeling the Formation of Lobate Debris Aprons on Mars by Creep of Ice-rich Permafrost Modeling the Formation of Lobate Debris Aprons on Mars by Creep of Ice-rich Permafrost

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja.....7809t&link_type=abstract

EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #7809

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Scientific paper

A wide variety of mid- to high-latitude surface features on Mars has long been attributed to viscous creep and flow phenomena associated with near-surface ground ice. These landforms fall into two classes: (1) softened terrain, which results from in situ viscous deformation and is evident in impact craters with degraded rims and flattened topographic profiles, and (2) debris aprons, which are produced by mass wasting along escarpments, e.g., lobate debris aprons, lineated valley fill, and concentric crater fill. Such features have been linked to kilometer-thick layers of ice-rich permafrost, an interpretation that is consistent with recent GRS observations indicating a high water ice content in the very shallow Martian subsurface. We are using MOC and MOLA data to document the characteristics of softened landforms and debris aprons east of Hellas. By comparing the observed landforms to the results of finite-element models of viscous creep relaxation, we can constrain the conditions necessary to allow such deformation on Mars. We have simulated the formation of debris aprons by creep of an ice-rich surface layer, incorporating recent measurements of the rheological parameters for dust/water ice mixtures. Our simulations demonstrate that the final morphology of the debris apron is strongly dependent on the initial distribution of the ice-rich material. Furthermore, even under present Martian conditions, viscous creep can occur quite rapidly, 1000 - 10,000 yr. However, if the mobility of the ice is restricted by a surface layer that resists deformation, or the high volume fractions of ice inferred from GRS data to be present near the surface do not continue to significant depths, deformation timescales could be significantly longer.

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