SATELLITE AND GROUND-BASED ANALYSES OF TERRESTRIAL ROCK GLACIERS AS ANALOGS TO MARTIAN LOBATE DEBRIS APRONS

A number of geomorphologic features related to the presence of subsurface ice have been identified on Mars. These include lobate debris aprons, which are steep-sided spatulate or lobate features extending from local topographic highs. These features are considered analogous to terrestrial rock and debris-covered glaciers, a conclusion supported by the identification of ice lenses underneath some debris aprons via satellite radar imaging. Thermophysical properties of debris aprons, derived from nighttime thermal infrared data, exhibit variations in thermal properties related to downslope flow of material, including lineations parallel to flow direction and curvilinear variations indicating flow compression near feature margins.

Thermophysical studies of terrestrial rock glaciers suggest similar variations, although at a smaller scale due to the small size of terrestrial features relative to those on Mars. A survey of apparent thermal inertia images derived from visible and thermal infrared satellite data suggests that observed thermophysical surface variations may be related to the relationship of ice and rock in the interior. Typical features on rock glaciers include downslope parallel lineations and lobate lineations corresponding to compressional flow ridges near the toe. More pronounced variations, typically curvilinear, are associated with debris-covered glaciers. Although ice occurs at depths well below the diurnal skin depth to which these measurements are sensitive, there appear to be variations in surface characteristics that are indicative of the relationship of ice and rock in the feature's interior.

A field study of the thermophysical properties of an inactive rock glacier (Lone Mountain, Montana) suggests that ground-based thermal imaging may be necessary to bridge the scale gap between smaller terrestrial features and Martian lobate debris aprons. Differences in response to solar heating were identified in thermal images of the feature and can be correlated with different surface properties such as slope, particle size, packing, and lichen cover.

These initial results suggest that further thermal studies of terrestrial rock glaciers would prove valuable for understanding the role subsurface ice has played in the formation of geomorphologic features on the surface of Mars.