Abstract The Hale impact crater is a large complex crater ( c. 150 × 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.

We present landforms on Svalbard (Norway) as terrestrial analogs for possible Martian periglacial surface features. While there are closer climatic analogs for Mars, e.g., the Antarctic Dry Valleys, Svalbard has unique advantages that make it a very useful study area. Svalbard is easily accessible and offers a periglacial landscape where many different landforms can be encountered in close spatial proximity. These landforms include thermal contraction cracks, slope stripes, rock glaciers, protalus ramparts, and pingos, all of which have close morphological analogs on Mars. The combination of remote-sensing data, in particular images and digital elevation models, with field work is a promising approach in analog studies and facilitates acquisition of first-hand experience with permafrost environments. Based on the morphological ambiguity of certain landforms such as pingos, we recommend that Martian cold-climate landforms should not be investigated in isolation, but as part of a landscape system in a geological context.

Numerous landforms with traits that are suggestive of formation by periglacial processes have been observed in Utopia Planitia, Mars. They include: small-sized polygons, flat-floored depressions, and polygon trough or junction pits. Most workers agree that these landforms are late Amazonian and mark the occurrence of near-surface regolith that is (was) ice rich. The evolution of the Martian landforms has been explained principally by two disparate hypotheses. The first is the “wet hypothesis.” It is derived from the boundary conditions and ice-rich landscape of regions such as the Tuktoyaktuk Coastlands, Canada, where stable liquid water is freely available as an agent of landscape modification. The second is the “dry” hypothesis. It is adapted from the boundary conditions and landscape-modification processes in the glacial Dry Valleys of the Antarctic, where mean temperatures are much colder than in the Tuktoyaktuk Coastlands, liquid water at or near the surface is rare, and sublimation is the principal agent of glacial mass loss. Here, we (1) describe the ice-rich landscape of the Tuktoyaktuk Coastlands and their principal periglacial features; (2) show that these features constitute a coherent assemblage produced by thaw-freeze cycles; (3) describe the landforms of Utopia Planitia and evaluate the extent to which “wet” or “dry” periglacial processes could have contributed to their formation; and (4) suggest that even if questions concerning the “wet” or “dry” origin of the Martian landforms remain open, “dry” processes are incapable of explaining the origin of the ice-rich regolith itself, from which the landforms evolved.

Abstract Permafrost is ground (soil or rock and included ice and organic material) that remains at or below 0 °C for at least two consecutive years. Permafrost terrain consists of an “active layer” at the surface that freezes and thaws each year, underlain by perennially frozen ground. The top of permafrost is at the base of this active layer. The base of permafrost occurs where the ground temperature rises above 0 °C at depth ( Osterkamp and Burn, 2002 ). In some cases, temperature measurements over a period of two years are required to determine the presence or absence of permafrost. Temperature measurements are also required to determine the status of the permafrost. Permafrost that is warm and/or warming is in danger of thawing. Approximately 25% of the exposed land area of Earth and ~80% of Alaska are underlain by permafrost. Mountain permafrost occurs at high elevations in western North America and on Mount Washington in New Hampshire. Permafrost has also been found near the summit of Mauna Kea in Hawaii. Permafrost is a product of cold climates. The first permafrost on earth must have existed prior to or formed coincidentally with the first glaciation, ~2.3 billion years ago. Permafrost occurrences, distribution, and thicknesses must have increased during periods of cold climates and decreased during warm intervals. Permafrost may have disappeared in the Arctic ~50 million years ago. The current permafrost in Alaska appears to have been initiated during the climatic cooling that began ~2.5 million years ago. During the past

We investigate the fate of permafrost since the Last Glacial Maximum in the Laptev and East Siberian Seas, a submergent coastal environment. The shelf here is up to 700 km wide and less than 80 m deep, a large area highly sensitive to changes in environmental conditions. Climate and sea-level histories and the terrestrial and coastal geomorphology of the region are combined with direct observations from drilling campaigns to review existing notions on the distribution, thickness, physical state, and history of the development of terrestrial and offshore permafrost since the Last Glacial Maximum. Drilling transects running perpendicular to the coast in the nearshore zone show that the interface between unfrozen and frozen sediments varies in its angle of inclination as a result of a number of factors, primarily coastal retreat rate. A conceptual model of permafrost development prior to submergence suggests that thermokarst and nearshore processes are critical in altering the development of permafrost in the submarine environment.