Evidence of ancient continental glaciation in the Martian northern plains

Abstract

Whorled ridges, spaced about 2–6 km and forming lobate patterns with lobe widths of about 150 km, occur at many locations in the northern plains of Mars, commonly in close association with sinuous troughs that contain medial ridges. These landforms resemble moraines, tunnel channels, and eskers found in terrestrial glacial terrains, such as the midcontinent of North America. Some Martian landscapes may have formed by disintegration of continental glaciers that covered much of the northern plains into the early Amazonian (i.e., late in Martian geologic history). Meltwater processes apparently were important in the collapse of these hypothesized ice sheets; hence, the glaciers apparently were wet based in part. Whereas striking similarities exist among areas of the northern plains and some glaciated Pleistocene terrains on Earth, there are also important differences; notably, drumlin fields, such as those in many glacial landscapes on Earth, are rare, absent, or not yet resolved in images of the Martian northern plains. Another major difference is that postglacial fluvial and other water‐related modifications (especially erosion) of Pleistocene terrains are substantial, but similar modifications are not observed in the northern plains; a virtually complete and sudden decline in the activity of liquid surface water following glaciation in the northern plains seems to be implied. The climatic implications of the hypothesized Martian glaciers and their decline are unclear. We investigate two possibilities, alternatively involving a relatively warm paleoclimate and the modern Martian climate. The hypothesized ice sheets in the basins within the northern plains (generally at elevations lower than −1 km) suggest a relationship of these frozen bodies of water with former regional lakes or seas, which may have formed in response to huge discharges of water from Martian outflow channels. This possible relationship has been modeled. Glaciers may have evolved from seas by their progressive freezing and then grounding and sublimational redistribution of sea ice. The transition to glaciation may have taken several million years if the climate was very cold, comparable to today's, or tens of thousands of years if the climate was as warm as modern Antarctica. A glacierized sea may have involved an extended period of glaciolacustrine and ice shelf processes.

The State and Future of Mars Polar Science and Exploration

“…Although the interpretation of specific features is often debated, there is a substantial consensus that periglacial processes (involving regolith creep, rock fracturing by freeze-thaw, and related processes) have been important in the geomorphic development of the surface. More controversial are proposals that true glacial processes (involving thick, self-deforming ice sheets) were widespread on Mars (Lucchitta 1982, Battistini 1987, Tricart 1988, Baker et al 1991, Kargel and Strom 1992, Kargel et al 1995. This is especially true of paleoclimatic interpretations of possible glacial features, estimates of the volume of ice that may have been involved, and speculation regarding the ultimate fate of that nowmissing H20.…”

Geological Processes and Evolution

“…If there were standing bodies of water in the northern lowlands in the past, under current climate conditions such lakes or oceans would rapidly freeze and form an ice cover (e.g., Kargel et al, 1996;Clifford and Parker, 1999). However they could stabilize if fed by meltwater or groundwater (McKay and Davis, 1991).…”

The fluvial history of Mars

“…Ghost craters in low parts of the northern plains suggest the presence of effluent deposited during the floods [54]. Many landforms in the lower areas of the northern plains have been compared with terrestrial features that form by meltwater under a static ice sheet [55] that could have been a frozen remnant of an ocean. There are thus several lines of evidence suggestive of the former presence of large bodies of water.…”