JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. E4, 8032, doi:10.1029/2002JE001864, 2003
[43] Determining the origin of ice in extant, active, rock glaciers on Earth is difficult. Topography, because of equifinality of form, will not uniquely distinguish between ice of glacier or permafrost origin. This means that analogue identification of features on Mars cannot be used to determine ice presence. A further complication arises where large landslides (Bergsturz, Sturzstroms) also give topography which may be similar to rock glacier forms. It should be possible to use MOLA altimetry to identify some detailed features which may be helpful to provide more critical criteria. These are, by analogy with terrestrial features: lateral ridges, “spoon-shaped hollows” in the corrie head (Figures 4a, 4b, 4c, 4d, 5a, 5b, 5c, and 5d) and concavities between stable lateral ridges as well as the detailed ridges and furrows of protalus lobes.
[44] Protalus lobes, or similar forms, appear to be found on Mars. Terrestrial protalus lobes do suggest a possible permafrost origin. However, it is possible that snowbank accumulation below cliffs, when covered with debris falls from cliffs above can give rise to these ridge systems. A unique indicator cannot be used here either. Using terrestrial analogues for features on Mars has considerable difficulties, accentuated when the Earth-bound features are themselves both difficult to interpret and indeed, sometimes in dispute. MOLA data from a variety of identified rock glacier and protalus lobe types may help to discriminate between landforms as well as provide test sites for future investigations.
[45] The advent of new orbital sensors using a variety of investigative techniques may help to determine and distinguish ice origins. In particular, MARSIS could be particularly helpful in determining the presence and location of ice bodies, although interpretation of terrestrial GPR data shows that appropriate models of ice location need to be devised to analyze the imagery. One way to progress would be with careful mapping on digital terrain models and map the features using Geographical Information Systems methodologies to look for patterns in location and type of feature. This approach may give a better overall understanding of the distributions of these complex features as thermally zoned or age differentiated.
Citation: , Rock glaciers and protalus landforms: Analogous forms and ice sources on Earth and Mars, J. Geophys. Res., 108(E4), 8032, doi:10.1029/2002JE001864, 2003.