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