Periglacial complexes and the deductive evidence of ‘wet’-flows at the Hale impact crater, Mars

The Hale impact crater is a large complex crater (c. 150 x c. 125 km) in the southern hemisphere of Mars. Recurring slope lineae have been observed on its central-peak slopes, as have relatively youthful gully-like landforms; the latter are observed adjacent to or in the midst of the former, as well as on all of the rim-material slopes. Three of the gullied slopes on the northern- rim materials exhibit landscape features that, on Earth, are synonymous with wet periglaciation, i. e. landscape modification by the freeze-thaw cycling of water. These features include: (1) gelifluction-like lobes; (2) patches of surface polygonization, possibly underlain by ice wedges and formed by thermal-contraction cracking; and (3) shallow, rimless and polygonized basins morphologically akin to terrestrial alases. Here, we use the spatial association of the gully-like landforms together with the putatively wet periglacial assemblages or complexes to deduce and ascribe, albeit indirectly, a wet origin to the former.