The low gravity present on Mars likely moved ice sheets very differently compared to Earth, leaving behind a less eroded surface.
Since Mars lacks glacial valleys, scientists believed that ancient ice masses on the Red Planet must have remained frozen to the ground, remaining motionless throughout the planet’s history. A variety of valleys and fjords have been carved into the surface of the Earth by the weight and grinding movement of glaciers. In view of Mars’ lack of similar terrain, researchers believe ancient ice masses were firmly frozen. However, according to new research, they weren’t stuck and were simply moving slowly. Glaciers are defined by their motion. During glacier and ice sheet melting, meltwater pools below and lubricates their downward slides.
According to this new study, Mars’ low gravity affects how rapidly an ice sheet slides and how water drains underneath it, leading to the formation and persistence of under-ice channels. The interface between rock and ice would become more frictional if water drains quickly. As a result, even when water accumulated under the ice sheet on Mars, the ground was eroded at extremely slow rates, the authors report. There is an incredibly nonlinear nature to ice. With the presence of water under former ice sheets on Earth and Mars, the feedbacks between glacial motion, glacial drainage, and glacial erosion would result in fundamentally different landscapes,” said Anna Grau Galofre, lead author of the new study, which was conducted while she was a postdoc at Arizona State University, and a planetary scientist at Laboratoire de Planétologie et Géosciences (LPG/CNRS/ Nantes Université/ Le Mans Université/Universtié d’Angers).
There are other geologic traces suggesting glacier-like ice masses in Mars’ past, including gravel ridges known as eskers and potential subglacial channels, Grau Galofre said, even though Mars does not have obvious U-shaped valleys similar to Earth’s glacial landscape. Compared to Earth, where you find drumlins, lineations, scouring marks, and moraines, Mars has channels and esker ridges under an ice sheet of precisely the same characteristics, Galofre said.
A team of researchers conducted a simulation of the dynamics of two equivalent ice sheets on Earth and Mars with similar thicknesses, temperatures, and availability of subglacial water. By applying an existing physical framework, coupled with ice motion dynamics, they were able to model Martian conditions using the drainage of water accumulated under Earth’s ice sheets. Their goal is to find out whether subglacial drainage will evolve into efficient drainage configurations or inefficient drainage configurations and how this will affect glacial sliding velocity and erosion on Mars.
Grau Galofre is of the opinion that, at some point, the interaction between ice masses and basal water must have taken place on Mars. In the early days, Mars may have had surface liquid water, extensive ice sheets, and volcanism, but today it has a global cryosphere, excluding the extensive ice sheets and volcanism it once had. Since Mars has a large water inventory, large topographic variations, liquid, and frozen water, volcanism, and is situated farther from the Sun than Earth, it is hard to believe that it never developed the conditions to grow ice sheets with subglacial water for 4 billion years of its planetary history, researchers explained.
According to this modeling effort, glacial ice masses would drain their basal meltwater much more efficiently on Mars than on Earth, which would prevent any lubrication of the base of ice sheets that would enhance glacial erosion and maintain fast sliding rates. The study suggests that typical lineated landforms found on Earth would not survive on Mars. Moreover, the findings may have implications for how ancient life may have survived on Mars, according to the authors. In the absence of a magnetic field, an ice sheet could provide a steady supply of water, stability, and protection for subglacial water bodies, protection from solar radiation, and insulation against extreme temperatures.
Geophysical Research Letters published the study.
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