Washington, Nov 21 : NASA's Mars Reconnaissance Orbiter has detected vast Martian glaciers of water ice buried under protective blankets of rocky debris at much lower latitudes than any ice previously identified on the Red Planet.
Scientists analyzed data from the spacecraft's ground-penetrating radar and suggested 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 W. Holt of the University of Texas at Austin, 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," he added.
The detection of these glaciers may also provide an answer to a Martian puzzle.
Scientists have been puzzled by what are known as aprons, which are gently sloping areas containing rocky deposits at the bases of taller geographical features, since NASA's Viking orbiters first observed them on the Martian surface in the1970s.
One theory has been that the aprons are flows of rocky debris lubricated by a small amount ice.
Now, the shallow radar instrument on the Mars Reconnaissance Orbiter has provided scientists an answer to this Martian puzzle.
"These results are the smoking gun pointing to the presence of large amounts of water ice at these latitudes," said Ali Safaeinili, a shallow radar instruments team member with NASA's Jet Propulsion Laboratory in Pasadena, California.
Radar echoes received by the spacecraft indicated radio waves pass through the aprons and reflect off a deeper surface below without significant loss in strength.
That is expected if the apron areas are composed of thick ice under a relatively thin covering.
The apparent velocity of radio waves passing through the apron is consistent with a composition of water ice.
According to Roberto Seu, leader of the instrument science team at the University of Rome La Sapienza in Italy, "It is now a priority to observe other examples of these aprons to determine whether they are also ice."