Huge water ice reservoirs are not exclusively present in Mars’ polar regions, according to the latest data sent by NASA’s Mars Reconnaissance Orbiter. The spacecraft, which is on a quest of finding evidence that water persisted on the surface of Mars for a long period of time, revealed glaciers of water ice under protective blankets of rocky debris, at much lower latitudes than ever identified before on the fourth planet from the Sun.

With the help of the Mars Reconnaissance Orbiter’s ground-penetrating radar, scientists found large buried glaciers, which extend for dozens of miles from edges of mountains or cliffs in the eastern Hellas region. The glaciers appear to have been covered by a layer of surface debris, suggesting that they formed in a previous climate conductive to glaciations at middle latitudes, scientists explained in the article published in Science.

According to John W. Holt of the University of Texas, Austin, this is the largest reservoir of this kind ever identified on the Red Planet, and he gave as an example just one of the features examined, which is three times larger than the city of Los Angeles and up to one-half-mile thick, and there are many more like that. “In addition to their scientific value, they could be a source of water to support future exploration on Mars,” he explained.

For over three decades now, scientists have been trying to figure out the mystery behind the aprons (gently sloping areas with rocky deposits at the bases of taller geographical features) on Mars. Thanks to the observations of the Mars Reconnaissance Orbiter, they reached one conclusion: there are large amounts of water ice on Mars, even at such low latitudes.

In order to prove that there is indeed a thick layer of water ice under the surface, rather than just a thick layer of rock debris, scientists used radar echoes. They found that radio waves passing through the aprons reflected a deeper surface below without a significant loss in strength, which suggested there was a thick layer of water ice under a thin layer of rock deposits.

The scientists said they are planning on investigation more aprons, to see if the findings are consistent with what they saw here. “There is an even larger volume of water ice in the northern deposits,” JPL geologist Jeffrey J. Plaut said. “The fact that 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.”

The discovery is of extreme importance, especially since these buried ice glaciers could in fact be fragments preserved from an ice age dating millions of years ago. This suggests that these glaciers could hold the key to a lot of secrets from Mars’ past that scientists are eager to uncover.