The surface of Mars can be a bumpy place, particularly in the mid-latitudes. There, steep peaks are often surrounded by broad lobes of material that stretch away from the peaks for up to a dozen miles.
Scientists have long thought that those big bumps might contain water ice, but in what form and how much no one knew.
New evidence from radar surveys by the Mars Reconnaissance Orbiter strongly suggest that the lobes are pure ice in the form of glaciers, buried under a thin layer of soil and rock. If so, there may be an enormous amount of ice on Mars apart from the poles, potentially providing a convenient resource for human missions.
“It’s sort of like discovering Greenland,” said John W. Holt of the University of Texas, lead author of a study in Science describing the findings.
The spacecraft’s ground-penetrating radar instrument, aimed at several of these lobes in the Hellas basin in the southern hemisphere, picked up two reflected signals — one from the surface and another from something else underground. “That can really only happen with a limited number of materials,” Dr. Holt said, and all the evidence pointed to massive sheets of ice.
The researchers suggest that the Hellas glaciers may have formed millions of years ago, when the planet’s spin axis was tilted more than today, resulting in a climate that produced a lot of snow in the region. This may have produced ice sheets that, by moving at some point, essentially buried themselves in debris, allowing the ice to survive. “The study shows that you can preserve a lot of ice for a long time under a relatively thin layer of cover,” Dr. Holt said.