Glaciers buried beneath the surface of Mars could contain enough water to cover the entire planet.
Glaciers were first confirmed on the Red Planet in 2008 and last year scientists from Bryn Mawr College and the Freie Universitaet Berlin found mineralogical evidence of their existence in an area known as Valles Marineris on Mars.
Now, a study published in Geophysical Research Letters has calculated the size of those glaciers, and thus the amount of water contained in the mountains of ice found at the planet's central latitudes in the southern and northern hemispheres. Using radar observations combined with ice flow modeling, the authors found that about 150 billion cubic meters of ice are contained in the glaciers - equivalent to a 1.1 meter layer of ice covering Mars.
That amount of ice would be a drop in the bucket on Earth - representing only 5 percent of the ice on Greenland.
The researchers took advantage of a project last year by University of Texas researchers that mapped the glaciers on the Red Planet. From there, the researchers were able to look at the radar data from a few areas, which helped them estimate the thickness of the ice.
"We have looked at radar measurements spanning ten years back in time to see how thick the ice is and how it behaves," said Nanna Bjørnholt Karlsson, a postdoctoral researcher at the Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen and a co-author on the paper.
"A glacier is after all a big chunk of ice and it flows and gets a form that tells us something about how soft it is," she said. "We then compared this with how glaciers on Earth behave and from that we have been able to make models for the ice flow."
The latest research builds on earlier findings that used radar measurements from the NASA Mars Reconnaissance Orbiter to identify shapes of glaciers below the surface. That discovery explained the aprons - gently sloping areas containing rocky deposits at the bases of taller geographical features - which NASA's Viking orbiters first observed them on the Martian surface in the 1970s.
Since then, scientists have determined the glaciers contained frozen water. That ended a debate over whether the glaciers were made up of carbon dioxide, mud or water ice.
The glacier work is part of a larger bid to better understand the role that water once played on the planet. The presence of water is considered one of the most important finds on the Red Planet, since it is considered a key to life. Where there is water on Earth, for example, there is life.
Along with finding scars detailing past flash floods, scientist last month announced Mars once contained enough water to fill the Arctic Ocean. Using powerful telescopes to measure signatures of water in the planet's atmosphere, they estimated that in its youth, Mars would have probably had an ocean more than a mile deep covering almost half of its northern hemisphere.
Bjørnholt Karlsson said the latest findings demonstrate that the ice - which is being protected by a layer of dust and rocks - was an important part of the "water reservoir" on Mars. She said the glaciers could shed light on the past and offer benefits to the future - providing a window into what the planet's climate looked like 5 million years ago and possibly providing a water source for a manned mission that is planned by 2030.
"An obvious question would be, why they have a specific distribution on the planet? Why are they not everywhere?" she said, adding that some previous studies have suggested the glaciers migrated from the poles. "We only see them within certain latitudes."
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