ROCK GLACIERS ON MARS

The objectives of our study are to 1) improve our understanding of the geomorphic controls on ridge and furrow topography on terrestrial rock glaciers; and 2) use this information to identify possible rock glaciers on Mars. Rock glaciers move by slip, flow and/or creep deformation that often produces distinctive ridges and furrows perpendicular to the flow direction. Recent findings from the gamma ray spectrometer aboard Mars Odyssey provide evidence that near-surface ground ice is abundant in the regions where suspected rock glaciers have been observed. Our study focused on rock glaciers in Yankee Boy Basin of the San Juan Mountains and Mt. Mestas of the Sangre de Cristo Range, both in Colorado. We seek to develop criteria to better identify rock glaciers on imagery from the Mars Global Surveyor Orbiter. We are also utilizing ground-penetrating radar (GPR) to discern the internal structure of a lobate rock glacier in Yankee Boy Basin for the purpose of better understanding the origin of ridges and furrows.

The spacing between ridges on terrestrial rock glaciers is most closely related to the gradient of rock glaciers and to the height of source areas for the rock debris. We are developing similar models for possible rock glaciers on Mars. Our GPR work revealed that the rock glacier in Yankee Boy Basin consists of parallel to sub-parallel units of layered ice-rich and ice-poor strata. Overlap exists in the major depositional units, corresponding to flow lobes. Layers within these units have been deformed primarily by folding. These features are consistent throughout the entire thickness of the rock glacier. Our search for rock glaciers on Mars has focused on latitudes above 35 degrees, including the Argyre and Hellas impact basins; Deuteronilus and Protonilus Mensae in the fretted terrain; and the volcanic mountains of Hecates Tholus and in the region north of Olympus Mons. A particularly strong candidate for a rock glacier exists in the central region of Dao Vallis.