Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images

[1] A unique morphology suggestive of viscous flow of a meters-thick surface layer was identified in high-resolution (<10 m/pixel) Mars Orbiter Camera (MOC) images. A global survey of 13,000 MOC images resulted in the identification of 146 images exhibiting these viscous flow features. Slope angles derived from Mars Orbiter Laser Altimeter (MOLA) data, along with an experimentally derived flow law for ice, were used to estimate the shear stress and assess the plausibility that a 10 m thick ice-dust mixture could produce the observed viscous deformation on timescales in agreement with the estimated age (10–10 years) of the material. Our shear stress estimates of 10 –10 2.5 MPa yield strain rates on the order of 10 –10 16 s , which are within the superplastic flow regime of ice. Mean annual surface temperatures, age constraints, and strain estimates show that it is possible for a meters-thick ice-dust mixture to undergo viscous deformation under past or present surface conditions for ice grain sizes >10 mm. The meters-thick layer in which the viscous flow features formed is morphologically similar to a degraded meters-thick ice-dust surface deposit (dissected mantle terrain). Locations of the viscous flow features, dissected mantle terrain, and recent gullies are concentrated in the midlatitude regions, and all three show identical distributions as a function of latitude, with the maximum frequency of occurrence at 40 N and S. The strong association between these small-scale flow features and the dissected mantle terrain, large-scale viscous flow features, and recent gullies imply that deposition, deformation, and removal of ice-rich materials has played an important role in the modification of the surface in the midlatitudes of Mars during the Amazonian and possibly longer.