Ancient glaciers on Mars flowed so slowly that we can hardly tell they flowed at all

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(ORDO NEWS) — On Earth, changes in our climate have caused glaciers to advance and retreat throughout our geologic history (known as glacial and interglacial periods).

The movement of these glaciers has carved out features on the surface including U-shaped valleys, hanging valleys and fjords. These features are absent on Mars, leading scientists to conclude that any glaciers on its surface were stationary in the distant past.

However, a new study by a team of American and French planetary scientists suggests that the Martian glaciers were indeed moving. slower than on earth.

The study was carried out by a team of geologists and planetary scientists from the School of Earth and Space Exploration (SESE) of Arizona State University (ASU) and the Laboratory for Planetary and Geosciences (LPG) at the University of Nantes in France.

The study was led by Anna Grau Galofre, 2018 SESE Fellow (currently at LPG), who was a postdoc at ASU when it was conducted.

A study titled “Valley Networks and the Glacial Record of Ancient Mars” recently appeared in the journal Geophysical Research Letters.

According to the USGS definition, a glacier is “a large, perennial accumulation of crystalline ice, snow, rock, sediment, and often liquid water that originates on land and moves downslope under its own weight and gravity.”

The key word here is the movement that results from the accumulation of melt water under the ice sheet and lubricates its movement down the landscape. On Earth, glaciers have advanced and retreated regularly over millennia, leaving behind boulders and debris and carving details into the surface.

For the sake of their research, Grau Galofre and her colleagues modeled how Martian gravity would work. affect the feedback between the speed of the ice sheet and how water flows under it. Faster water drainage would have increased friction between rock and ice, leaving channels under the ice that would likely persist over time.

The absence of these U-shaped valleys means that the ice sheets on Mars have likely moved and eroded the surface. the ground beneath them is happening extremely slowly compared to what is happening on earth.

However, scientists have found other geological traces that suggest that there was glacial activity on Mars in the past. These include long, narrow, winding ridges composed of layered sand and gravel (eskers) and other features that may result from subglacial channels.

Grau Galofre said in a recent AGUNews press release:

“Ice is incredibly non-linear. Feedbacks associated with glacier movement, glacial runoff and glacial erosion will lead to fundamentally different landscapes associated with the presence of water under the former ice sheets on Earth and Mars.

While on Earth you will get drumlins, lines, scour marks and moraines, on Mars you will typically get channels and esker ridges under the ice sheet with exactly the same characteristics.”

To determine if Mars has had glacial activity in the past, Grau Galofre and her colleagues modeled the dynamics of two ice sheets on Earth and Mars that had the same thickness, temperature, and subglacial water.

They then adapted the physical basis and dynamics of the ice flow, which brought the flow of water under the land cover to Martian conditions.

From this, they learned how subglacial drainage would develop on Mars, what effect it would have on the speed at which glaciers slide across the landscape, and the erosion it might cause.

These results indicate that glacial ice on Mars will drain melt water much more efficiently than glaciers on Earth.

This would largely prevent the base of the ice sheets from being lubricated, resulting in higher slip rates and increased erosion caused by glaciers.

In short, their study showed that linear landforms on Earth, associated with glacial activity, did not have time to develop on Mars.

Grau Galofre said:

“From early Mars with surface liquid water, vast ice sheets and volcanism to the global cryosphere that Mars is now, interaction between ice masses and basal water must have happened at some point.

It’s just very hard to believe that in 4 billion years of planetary history, Mars has never been able to grow ice sheets with subglacial water, because it’s a planet with vast water reserves, great topographical variation, both liquid and frozen water, volcanism, [and] located farther from the Sun than the Earth.”

In addition to explaining why Mars lacks certain glacial features, the work also has implications for the possibility of life on Mars and whether that life can survive the transition to a global cryosphere that we are seeing today.

According to the authors, the ice sheet could provide a stable water supply, protection and stability to any subglacial reservoirs where life could arise. They will also protect against solar and cosmic radiation (in the absence of a magnetic field) and insulate against extreme temperature fluctuations.

These results are part of a growing body of evidence that life has existed on Mars and survived. long enough to leave evidence of its existence.

It also indicates that missions such as Curiosity and Perseverance, which will be joined in the near future by ESA‘s Rosalind Franklin rover and other exploration robots, are searching in the right places.

Where water once flowed in the presence of slowly retreating glaciers, microbial life forms that evolved when Mars was warm and humid (about 4 billion years ago) may have survived when the planet got colder. and dried up.

These results may also reinforce the suggestion that as this transition progressed and much of Mars’ surface water retreated underground, potential life on the surface followed.

So future missions to explore Mars’ vast deposits of water minerals (recently discovered by ESA) may be the ones that will finally find evidence of modern life on Mars!


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