On earth, changes in our climate have caused glaciers to advance and retreat throughout our geological history (known as glacial and interglacial periods). The movement of these glaciers has carved features into the surface, including U-shaped valleys, hanging valleys, and fjords. These features are missing on Mars, leading scientists to conclude that the glaciers on its surface in the distant past were stationary. However, new research by a team of American and French planetary scientists suggests that Martian glaciers moved more slowly than those on Earth.
The research was carried out by a team of geologists and planetary scientists from the School of Earth and Space Exploration (SESE) at Arizona State University (ASU) and the Laboratorie du Planétologie et Géosciences (LPG) at the University of Nantes. in France. The study was led by Anna Grau Galofre, a 2018 exploration fellow with SESE (currently at LPG), who was a postdoc at ASU when it was conducted. The study, titled “Valley Networks and the Record of Glaciation on Ancient Mars,” recently appeared in the Geophysical Investigation 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 downhill under the influence of its own weight and gravity.” ”. The keyword here is does it move, resulting from meltwater accumulating beneath the ice sheet and lubricating its path downward across the landscape. On Earth, glaciers have regularly advanced and retreated for eons, leaving rocks and debris in their wake and carving features into the surface.
For the sake of their study, Galofre and colleagues modeled how Martian gravity would affect the feedback between how fast an ice sheet moves and how water drains out from under it. Faster water drainage would increase 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 likely moved and eroded the ground beneath them at an extremely slow rate compared to what occurs on Earth. However, scientists have found other geological clues that suggest there was glacial activity on Mars in the past.
These include long, narrow, sinuous ridges composed of layered sand and gravel (eskers) and other features that could be the result of subglacial channels. Said Galofre in a recent AGUNews press release:
“Ice is incredibly nonlinear. Feedbacks linking glacial movement, glacial drainage, and glacial erosion would result in fundamentally different landscapes related to the presence of water beneath ancient ice sheets on Earth and Mars. Whereas on Earth you would have drumlins, lineations, erosion marks and moraines, on Mars you would tend to have channels and esker ridges under an ice sheet of exactly the same characteristics.”
To determine whether Mars experienced glacial activity in the past, Grau Galofre and colleagues modeled the dynamics of two ice sheets on Earth and Mars that had the same thickness, temperature, and availability of subglacial water. They then adapted the physical framework and ice flow dynamics that describe the drainage of water under the Earth’s layers to Martian conditions. From this, they learned how subglacial drainage would evolve on Mars, what effects this would have on the speed at which glaciers slid across the landscape, and the erosion this would cause.
These findings demonstrate how glacial ice on Mars would drain meltwater much more efficiently than glaciers on Earth. This would largely prevent lubrication at the base of the ice sheets, leading to faster slip rates and increased erosion by glaciers. In short, their study showed that Earth-aligned landforms associated with glacial activity would not have had time to develop on Mars. Grau Galofre said:
“Going from an early Mars with the presence of liquid surface water, extensive ice sheets and volcanism to the global cryosphere that is Mars today, the interaction between the ice masses and the basal water must have occurred at some point. It is very difficult to believe that throughout 4 billion years of planetary history, Mars never developed the conditions for ice sheets to grow with the presence of subglacial water, since it is a planet with an extensive inventory of water, large variations topographical, presence of both liquid and water. frozen water, volcanism, [and is] located farther from the Sun than the Earth.”
As well as explaining why Mars lacks certain glacial features, the work also has implications for the possibility of life on Mars and whether that life could survive the transition to a global cryosphere that we see today. According to the authors, an ice sheet could provide a constant supply of water, protection and stability to any body of subglacial water where life might have arisen. They would also protect against solar and cosmic radiation (in the absence of a magnetic field) and insulate against extreme temperature variations.
These findings are part of a growing body of evidence that life existed on Mars and survived long enough to leave behind evidence of its existence. It also indicates that missions like Curiosity Y Perseverance, to which will be added that of the ESA rosalind franklin rover and other robotic explorers in the near future are looking in all the right places. Where water once flowed in the presence of slowly retreating glaciers, the microbial life forms that arose when Mars was hot and humid (about 4 billion years ago) may have persisted as the planet cooled and desiccated. .
These findings may also bolster speculation that as this transition progressed and much of Mars’ surface water receded underground, potential life on the surface followed. As such, future missions investigating Mars’ extensive aqueous mineral deposits (recently mapped by ESA) could be the ones that finally find evidence of life on Mars today!
This article was originally published on universe today by Matt Williams. Read the original article here.