Ice sheets once covered Mars
Mars, our closest planetary neighbor, is currently the target of several missions. Remotely controlled vehicles should explore the planet extensively, take samples and continue to search for water. It is assumed that the distinctive valleys and incisions on the Martian surface were once formed by masses of water and that the planet was warm and humid, at least in its early stages. However, this picture does not seem to be entirely correct: the valleys, especially in the southern highlands, were created by gigantic ice sheets and underlying outflows, a new analysis concludes.
The work of the Canadian research group analyzed images of more than 10,000 valleys on Mars using a newly created algorithm to discover the erosion processes that led to their formation. They compared these valleys with those located in the Arctic and Antarctic regions. Especially those on Devon Island, an island in the north of Nunavut, were very similar to the valleys on Mars. “Devon Island is one of the best analogues we have for Mars here on Earth,” explains co-author Gordon Osinski, a professor at the University of Western Ontario. “It is a cold, dry, polar desert, and the glaciation is largely cold-based.”
By analysing the results of the algorithm, the researchers conclude that the valleys in the southern highlands of Mars were largely not formed by rivers created by rain. Instead, the analysis and modelling of the Martian climate about 3.8 billion years ago shows a colder planet covered by ice sheets. Water flowed under the ice, the ice followed and then formed the valleys. “Climate modelling predicts that Mars’ ancient climate was much cooler during the time of valley network formation,” says postdoctoral researcher Anna Grau Galofre, the study’s lead author and currently employed by Arizona State University.
“Using the geomorphology of Mars’ surface to rigorously reconstruct the character and evolution of the planet in a statistically meaningful way is, frankly, revolutionary”
Professor Mark Jellinek, University of British Columbia
“We tried to put everything together and bring up a hypothesis that hadn’t really been considered: that channels and valleys networks can form under ice sheets, as part of the drainage system that forms naturally under an ice sheet when there’s water accumulated at the base.” The researchers have now been able to substantiate this hypothesis with their work. “Using the geomorphology of Mars’ surface to rigorously reconstruct the character and evolution of the planet in a statistically meaningful way is, frankly, revolutionary,” co-author Mark Jellinek, a professor at the University of British Columbia, describes the work. “TThe findings demonstrate that only a fraction of valley networks match patterns typical of surface water erosion, which is in marked contrast to the conventional view.”
But the work of the scientists goes further than expected. Because the algorithm, developed by Anna Grau Developed Galofre, can also be applied to Earth and help to learn more about the formation of global ice sheets in the early days of the glaciation of Antarctica and Greenland. “Currently we can reconstruct rigorously the history of global glaciation on Earth going back about a million to five million years,” explains Jellinek. “Anna’s work will enable us to explore the advance and retreat of ice sheets back to at least 35 million years ago, back in time well before the age of our oldest ice cores. These are very elegant analytical tools.”
Dr Michael Wenger, PolarJournal
Link to the study:
Grau Galofre, A., Jellinek, A.M. & Osinski, G.R. Valley formation on early Mars by subglacial and fluvial erosion. Nat. Geosci. (2020)
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