Chapter 8 - Slow Periglacial Mass Wasting (Solifluction) on Mars

Abstract

Hillslope lobate landforms on Earth, formed by slow creep in periglacial terrain, always involve the action of liquid water. This chapter reviews previous observations of small-scale lobate forms from the northern hemisphere of Mars and adds new observations from the southern mid- and high latitudes that have a similar morphology, scale, and geological setting to those on Earth. We suggest that these features represent some of the best evidence for the action of liquid water at or near the surface in the Late Amazonian Epoch. We searched all available 25cm/pix High-Resolution Imaging Science Experiment images (2007–13) from 40°S to 80°S. These newly reported small-scale lobes are extremely similar in morphology, morphometry, and setting to their northern counterparts and to their (possible) terrestrial counterparts. All martian lobes form at latitudes where near-surface ground ice is hypothesized and in close proximity to other landforms that might also indicate ground ice, such as small-scale polygonally patterned ground and gullies. We propose that a thaw-based hypothesis provides the best explanation for the assemblage of landforms and their geographical distribution. In this scenario gullies, patterned ground, and small-scale lobes may form a hydrologic continuum on slopes where available water content governs the type of landform produced.