The last global glaciation occurred on Earth about 20 thousand years ago, and geologists find traces of it all over the world. After analyzing the surface of Mars and using these observations, American scientists came to the conclusion that the Red Planet also went through several ice ages in the last 300 – 800 million years.
A scientific paper with such conclusions was prepared by Joseph S. Levy, a geologist from Colgate University in the state of New York. It is published in the peer-reviewed journal Proceedings of the National Academies of Sciences ( PNAS ) of the US National Academy of Sciences. In the course of the study, Levy used the help of his students, who also produced several supplementary articles as a result.
The logic is quite simple: during formation and subsequent contraction, glaciers leave characteristic footprints. As a rule, these are stones of different shapes and sizes, some of which make it easy to determine that they were frozen in ice. Together with the students, Joseph studied high-resolution images of the Martian surface for two years in a row, mostly on summer holidays, and their results have now changed everything we know about Mars’s past and its ice ages.
With the Mars Reconnaissance Orbiter ( MRO ) probe working hard on Mars for over 15 years, humankind has detailed photographs of the surface of the Red Planet with a resolution of 25 centimeters per pixel. In fact, in these pictures, you can see any object comparable in size to a large book. And Levy and his assistants cataloged boulders near 45 Martian glaciers.
And at first, the geologist wanted to take the easy way. They trained a neural network on terrestrial photographs and tried to apply it to Martian images. But it didn’t work: the AI gave too much error rate, so they had to use human labor. The second significant problem led to almost panic: the stones on Mars were distributed, at first glance, in a completely random way which is exactly the opposite of what was expected.
Martian glaciers are similar to terrestrial rock ones – something like concrete, in which rocks are bound by ice, like cement. In places of degradation, where the ice retreated, boulders and stones remain on the fairly sagging surface.
The farther from the current edge of the glacier, the smaller the rock fragments – they are destroyed due to erosion. And at the very edge, in turn, the boulders are larger. But on Mars, for some reason, all stones of different sizes are mixed. And that turned out to be a key clue.
Studying the large amount of data formed on the distribution of boulders along the path of glaciers, Levy discovered several patterns. In short, the stones freed from under the ice on the Red Planet are grouped. There are several of these groups – and, accordingly, the periods of retreat and subsequent re-formation of glaciers.
When images of higher resolution become available, it will be possible to refine the data obtained by American geologists. But even in its current version, the work of Colgate University specialists provides enough data for some serious thinking.
The fact is that, according to one of the dominant versions, the Martian glaciers were formed as a result of fluctuations in the inclination of the planet’s rotation. And if there have been several ice ages over the past 10-100 million years, as Levy estimates, then Mars in the recent past was extremely unstable.
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• Anderson, P. (n.d.). New evidence for multiple ice ages on Mars.
• Blanding, M. (n.d.). Colgate Planetary Geologist Publishes Groundbreaking Analysis of Mysterious Martian Glaciers.
• Levy, J., Fassett, C., Holt, J., Parsons, R., Cipolli, W., Goudge, T., . . . Armstrong, I. (2021, January 26). Surface boulder banding indicates Martian debris-covered glaciers formed over multiple glaciations.
• Wood, A. (2021, January 20). Glaciers on Mars likely didn’t form during a single ice age event.