Artist concept of glacier on Mars. Image credit: NASA/JPL [Photo: nasa.gov]

NASA's Mars Reconnaissance Orbiter has revealed vast Martian glaciers of water ice under protective blankets of rocky debris at much lower latitudes than any ice previously identified on Mars.

Scientists analyzed data from the spacecraft's ground- penetrating radar and report in the Nov. 21 issue of the journal Science that buried glaciers extend for dozens of miles from the edges of mountains or cliffs.

A layer of rocky debris blanketing the ice may have preserved the underground glaciers as remnants from an ice sheet that covered middle latitudes during a past ice age. This discovery is similar to massive ice glaciers that have been detected under rocky coverings in Antarctica.

"Altogether, these glaciers almost certainly represent the largest reservoir of water ice on Mars that is not in the polar caps," said John Holt of University of Texas, who is lead author of the report. "Just one of the features we examined is three times larger than the city of Los Angeles and up to half a mile thick. And there are many more. In addition to their scientific value, they could be a source of water to support future exploration of Mars."

The fact these features are in the same latitude bands, about 35 to 60 degrees in both hemispheres, points to a climate-driven mechanism for explaining how they got there, according to NASA geologist Jeffrey Plaut.