The Mars Reconnaissance Orbiter used ground-penetrating radar to discover numerous buried glaciers on Mars, covered with dirt and up to a half-mile thick. This is only the latest sign that life may be sustainable on Mars. John Holt of the University of Texas at Austin is the lead author (along with 11 co-authors) of the article describing these findings in the 11/21 issue of Science (vol 322, p 1235 by subscription).
NewScientist
The glaciers, found at latitudes between 30 and 60° in both the northern and southern hemispheres, sit underneath fields of rocky debris. The appearance of the landscape suggests the debris flowed from hills lying up to 20 kilometres away.
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The glaciers likely formed during a time when Mars's pole pointed more towards the Sun, says co-author James Head of Brown University in Providence, Rhode Island. Because Mars lacks a massive moon that can stabilise its tilt, the planet is thought to wobble dramatically every 120,000 years or so.
Houston Chronicle
Mars may undergo periodic climate swings linked to changes in its axis. During these changes, the north pole dips, exposing the region to higher temperatures, possibly thawing the ice.
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Water would prove valuable to future human explorers as well. Its chemical elements, oxygen and hydrogen, can be used as rocket propellants, and oxygen, of course, is a source of air for breathing.
"Altogether, these features almost certainly represent the largest reservoir of water ice on Mars that's not in the polar caps," Holt said.
Ali Safaeinili, a member of the research team from NASA's Jet Propulsion Laboratory, agreed. "These results are the smoking gun pointing to the presence of large amounts of water ice at these latitudes," he said.
Space.com
These mounds of ice exist at much lower latitudes than any ice previously found on the red planet.
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The gently sloping mid-latitude debris flows have puzzled scientists since they were revealed by NASA's Viking orbiters in the 1970s — they looked very different than the fans and cones of debris found near mountains and cliffs in Mars' equatorial regions.
Since their discovery, scientists have been debating how the features formed, with some proposing they were debris flows lubricated by ice that had since evaporated away. But more recent observations suggested that the features "might be more ice than rock," Holt said.
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The researchers estimate that the amount of ice in these mid-latitude glaciers is about 1 percent of the ice that's in Mars' polar caps — roughly equivalent to the ratio of Earth's non-polar glaciers to its polar ice, Holt told SPACE.com. The glaciers could hold as much as 10 percent of the ice in the polar caps, similar to comparing Greenland's ice sheets to Antarctica, Holt added.
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"On Earth," Head said, "such buried glacial ice in Antarctica preserves the record of traces of ancient organisms and past climate history."
Ancient ice layers in glaciers on Earth preserve the signature of the current atmosphere at the time that they formed. Head thinks the same could be true of the Martian glaciers. In particular, small bubbles that form as the ice layers are deposited could have "samples of the atmosphere at that time," he said.
A lander capable of drilling down several meters could be able to sample the ice in the glaciers.