Researchers discovered an ice sheet on Mars that looks bigger than Texas and California cities of US.
Ali Bramson, a graduate student in the University of Arizona's Lunar and Planetary Laboratory (LPL), first spotted the ice sheet when she was working with her colleagues, reports CBS News.
Bramson was onto something when she spotted a "crazy looking crater" on the face of Mars, the media reports.
"It's worth mentioning that terraced craters of this size are quite rare," Shane Byrne, an associate professor in LPL and a co-author with Bramson and several others on a paper about the discovery published this week in Geophysical Research Letters,a journal of the American Geophysical Union, told CBS News.
"But in this area of Mars (Arcadia Planitia), there are a lot of terraced craters," he said. "The craters may have formed at different times, but they all have terraces, which indicates something weird is going on in the subsurface."
In this case, there was ice - and lots of it. Beneath the surface, they discovered an enormous slab of water ice, measuring 130 feet thick and covering an area equivalent to that of California and Texas combined, the report said.
The ice was the result, the authors wrote, of snowfall "which can most easily explain the thickness and widespread nature of the excess ice observed."
The researchers turned to the Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment operated out of LPL to locate the ice.
They created three-dimensional models of the area's craters to measure the depth of their terraces and used the orbiter's Shallow Radar instrument to beam radar pulses to Mars to measure the time it took for the radar signals to penetrate the surface's buried layers and bounce back.
Bramson and her colleagues, by combining the two data sets, were able to determine that beneath the dirt surface, or regolith, was ice that was as much as 40 meters (131 feet) thick.
"This slab of ice right beneath the surface has been preserved for the last 10s of millions of years and is a remnant from a past climate since water ice isn't stable at the surface of Mars at this location today," Bramson told CBS News.
"It has undergone many periods where ice would be very unstable at these latitudes, and we would expect ice to sublimate away during those periods," she continued.
"Therefore, this discovery will allow us to look into the conditions necessary for the ice's long-term preservation. It will also inform us about what the Martian climate was like 10s of millions of years ago when it formed - that there was likely a lot of snowfall to build up a layer of ice this thick."