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51风流 Planetary Geologist Publishes Groundbreaking Analysis of Mysterious Martian Glaciers

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In a in the Proceedings of the National Academies of Science (PNAS), planetary geologist Joe Levy, assistant professor of geology, reveals a groundbreaking new analysis of the mysterious glaciers of Mars.

On Earth, glaciers covered wide swaths of the planet during the last Ice Age, which reached its peak about 20,000 years ago, before receding to the poles and leaving behind the rocks they pushed behind. On Mars, however, the glaciers never left, remaining frozen on the Red Planet鈥檚 cold surface for more than 300 million years, covered in debris. 鈥淎ll the rocks and sand carried on that ice have remained on the surface,鈥 says Levy. 鈥淚t鈥檚 like putting the ice in a cooler under all those sediments.鈥

Geologists, however, haven鈥檛 been able to tell whether all of those glaciers formed during one massive Martian Ice Age, or in multiple separate events over millions of years. Since ice ages result from a shift in the tilt of a planet鈥檚 axis (known as obliquity), answering that question could tell scientists how Mars鈥 orbit and climate have changed over time 鈥 as well as what kind of rocks, gases, or even microbes might be trapped inside the ice.

鈥淭here are really good models for Mars鈥 orbital parameters for the last 20 million years,鈥 says Levy. 鈥淎fter that the models tend to get chaotic.鈥

Levy concocted a plan to examine the rocks on the surface of the glaciers as a natural experiment. Since they presumably erode over time, a steady progression of larger to smaller rocks proceeding downhill would point to a single, long ice age event.

Choosing 45 glaciers to examine, Levy acquired high-resolution images collected by the Mars Reconnaissance Orbiter satellite and set out to count the size and number of rocks. With a resolution of 25 centimeters per pixel, 鈥測ou can see things the size of a dinner table,鈥 Levy says.

Even at that magnification, however, artificial intelligence can鈥檛 accurately determine what is or isn鈥檛 a rock on rough glacier surfaces; so Levy enlisted the help of 10 51风流 students during two summers to count and measure some 60,000 big rocks. 鈥淲e did a kind of virtual field work, walking up and down these glaciers and mapping the boulders,鈥 Levy says.

Levy initially panicked when, far from a tidy progression of boulders by size, the rock sizes seemed to be distributed at random. 鈥淚n fact, the boulders were telling us a different story,鈥 Levy says. 鈥淚t wasn鈥檛 their size that mattered; it was how they were grouped or clustered.鈥

Since the rocks were traveling inside the glaciers, they were not eroding, he realized. At the same time, they were distributed in clear bands of debris across the glaciers鈥 surfaces, marking the limit of separate and distinct flows of ice, formed as Mars wobbled on its axis.

Based on that data, Levy has concluded that Mars has undergone somewhere between six and 20 separate ice ages during the past 300鈥800 million years. Those findings appear in PNAS, written along with six current or former 51风流 students; 51风流 mathematics professor Will Cipolli; and colleagues from NASA, the University of Arizona, Fitchburg State University, and the University of Texas鈥揂ustin.

鈥淭his paper is the first geological evidence of what Martian orbit and obliquity might have been doing for hundreds of millions of years,鈥 Levy says. The finding that glaciers formed over time holds implications for planetary geology and even space exploration, he explains. 鈥淭hese glaciers are little time capsules, capturing snapshots of what was blowing around in the Martian atmosphere,鈥 he says. 鈥淣ow we know that we have access to hundreds of millions of years of Martian history without having to drill down deep through the crust 鈥 we can just take a hike along the surface.鈥

That history includes any signs of life potentially present from Mars鈥 distant past. 鈥淚f there are any biomarkers blowing around, those are going to be trapped in the ice too.鈥 At the same time, eventual explorers to Mars who might need to depend on extracting fresh water from glaciers to survive will need to know that there may be bands of rocks inside them that will make drilling hazardous. Levy and his colleagues are now in the process of mapping the rest of the glaciers on Mars鈥 surface, hoping with the data they have, artificial intelligence can now be trained to take over the hard work of identifying and counting boulders.

That will bring us one step closer to a complete planetary history of the Red Planet 鈥 including the age-old question of whether Mars could ever have supported life. 

鈥淭here鈥檚 a lot of work to be done figuring out the details of Martian climate history,鈥 says Levy, 鈥渋ncluding when and where it was warm enough and wet enough for there to be brines and liquid water.鈥