Erosion on Mars reveals ice, moves boulders

When we think of Mars, we think of a dry, desolate planet. But beneath the dust of Mars lies frozen water, and a new study has found that erosion is exposing that water ice.

Researchers using several satellites, including the Mars Reconnaissance Orbiter (MRO) and the High Resolution Imaging Science Experiment (HiRISE), have revealed eight locations of steep slopes, or scarps, all at mid-latitudes on the Red Planet. And that ice could be used as a potential resource by future visitors.

"What they show is slices through ice, in some places the ice is 100 metres thick and starts within a metre or two of the surface," Colin Dundas, a research geologist at the U.S. Geological Survey's Astrogeology Science Centre, told CBC News.

There are plans to get humans to Mars by the 2030s. Transporting water would be expensive: the heavier the payload atop a rocket, the more fuel is needed, which in turn increases the cost. Having a source on the planet would reduce costs and provide colonists with drinking water as well as water to grow food.

Using data from satellites and rovers that have been rumbling across the surface of the Red Planet, planetary astronomers believe that Mars was once a wet planet, with an ocean and rivers some 4.3-billion years ago. A 2015 study suggested the ocean was 1.6-kilometres deep near what is now the northern hemisphere.

But over time, the planet lost its atmosphere and thus, its surface water. However, ice does reside below the surface. In 2016, researchers found evidence to suggest one ice deposit holds as much water as Lake Superior.

The data suggests that the ice is not only strong, but bands and varying colours suggest that the ice contains layers, which could help scientists better understand how the climate on Mars has changed over its history.

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"I was surprised to find such good, large exposures,"  Dundas said. "We'd seen ice exposed by the craters ... but finding such clean exposures that weren't disrupted by an impact was quite surprising."

And the erosion that's taking place is changing the Martian landscape.

"One of the most interesting observations was seeing boulders fall out at one scarp, which suggested that it's actively sublimating or retreating, and also helped confirm that it was exposed ice and not surface frost," Dundas said.

The researchers say that the ice, which they believe could extend beyond what they've found, could be a useful source of water for future missions to Mars.

"Exactly how that plays into using water on Mars will be up to those who choose landing sites, but that's potentially useful information," Dundas said.