Glaciers flowed on ancient Mars, but slowly


Because of Mars’ unique conditions, its ancient glaciers likely flowed very slowly, according to a new study in Geophysical Research Letters. A range of ice features exist on the Red Planet today. Credit: NASA/JPL-CalTech/University of Arizona
Because of Mars’ unique conditions, its ancient glaciers likely flowed very slowly, according to a new study in Geophysical Research Letters. A range of ice features exist on the Red Planet today. Credit: NASA/JPL-CalTech/University of Arizona

Glaciers' weight and grinding action have etched different valleys and fjords onto the Earth's surface. Because Mars lacked comparable terrain, researchers assumed that ancient ice masses on the Red Planet were solidly frozen to the ground. According to a new study, they were not frozen in place but just moved very slowly. A glacier's definition includes movement. Meltwater collects beneath glaciers and ice sheets on Earth, lubricating the downhill fall of these ice rivers.


The new study examined how Mars' low gravity would alter the feedback between how quickly an ice sheet slides and how water drains beneath the ice, discovering that under-ice canals would emerge and remain. Fast water drainage would enhance friction at the rock-ice contact. According to the scientists, this suggests that ice sheets on Mars moved and destroyed the ground underneath them at extremely slow rates, even when water pooled beneath the ice. Geophysical Research Letters released the latest findings.


The principal author of the current study, Anna Grau Galofre, a planetary scientist at Laboratoire de Planétologie et Géosciences (LPG/ CNRS/ Nantes Université/ Le Mans Université/ Universitié d'Angers) and a postdoc at Arizona State University, stated, "Ice is incredibly non-linear." The feedback from glacial motion, drainage, and erosion would result in fundamentally different landscapes on Earth and Mars due to the existence of water beneath ancient ice sheets.


Although Mars lacks the conspicuous U-shaped valleys that characterize Earth's glacial landscapes, researchers have discovered additional geologic clues indicating glacier-like ice volumes in Mars' past, such as gravel ridges known as eskers and probable subglacial channels.

Glacial landscapes on Axel Heiberg Island (Canadian Arctic Archipelago) showing typical (glaciers) and atypical (subglacial channels, bottom right) glacial landscapes. Credit: A. Grau Galofre
Glacial landscapes on Axel Heiberg Island (Canadian Arctic Archipelago) showing typical (glaciers) and atypical (subglacial channels, bottom right) glacial landscapes. Credit: A. Grau Galofre

According to Grau Galofre, whereas on Earth you would find drumlins, lineations, scouring marks, and moraines, on Mars you would find channels and esker ridges with the same features.


Grau Galofre and her colleagues simulated the dynamics of two identical ice sheets on Earth and Mars with the same thickness, temperature, and subglacial water availability. They adapted an existing physical framework that describes the drainage of water accumulated beneath Earth's ice sheets, along with ice motion dynamics, to model Martian conditions and learn whether subglacial drainage would evolve toward efficient or inefficient drainage configurations, as well as the impact this configuration would have on glacial sliding velocity and erosion.


According to Grau Galofre, the interaction between ice masses and basal water must have occurred at some time during the transition from an early Mars with surface liquid water, vast ice sheets, and volcanism to the global cryosphere that Mars now is. It's difficult to believe that in 4 billion years of planetary history, Mars never developed the conditions for growing ice sheets in the presence of subglacial water, despite having an extensive water inventory, large topographic variations, both liquid, and frozen water, volcanism, and being farther from the Sun than Earth.


The results of this modeling study show how glacial ice masses on Mars would drain their basal meltwater far more efficiently than on Earth, virtually prohibiting any lubrication of the base of ice sheets, which would lead to high sliding rates and increased glacial erosion. According to this study, typical lineated landforms present on Earth would not have enough time to evolve on Mars. According to the authors, the finding holds ramifications for the survival of putative ancient life forms on Mars. An ice sheet might offer a constant source of water, protection and stability to any subglacial water bodies such as lakes, shielding from solar radiation in the absence of a magnetic field, and insulation from significant temperature changes.

Journal Information: A. Grau Galofre et al, Valley Networks and the Record of Glaciation on Ancient Mars, Geophysical Research Letters (2022). DOI: 10.1029/2022GL097974
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