Massive Reserve of Ice Found Near Equator of Mars

Deep beneath Mars' equator lies what is believed to be a supply of frozen water that, if melted, would cover the entire planet in an ocean of at least 5 feet deep. That's according to the European Space Agency, whose Mars Express spacecraft discovered the suspected reserve of water ice—the largest detected near the Red Planet's equator so far—while in orbit around Mars. "We don't expect to see a polar ice cap at the equator," ESA project scientist Colin Wilson explains, per Euronews. "Excitingly, the radar signals match what we expect to see from layered ice and are similar to the signals we see from Mars' polar caps, which we know to be very ice rich," says Thomas Watters of the Smithsonian Institution, lead author of a study published in Geophysical Research Letters.

The good news is that there looks to be a lot of ice, some 2.3 miles thick, and at low latitudes, where future astronauts would be expected to land. The bad news is that the deposits are "topped by a crust of hardened ash and dry dust" that extends for hundreds of meters, per Space.com. They're also "heavily contaminated by dust." Experts initially considered the frozen water might be dust when Mars Express' subsurface radar MARSIS first detected the deposits beneath the Medusae Fossae Formation (MFF), a geological formation separating the northern highlands and southern lowlands, in 2007. But new observations indicate something far more exciting lies in wait.

"Given how deep it is, if the MFF was simply a giant pile of dust, we'd expect it to become compacted under its own weight" and "create something far denser than what we actually see," says study co-author Andrea Cicchetti of Italy's National Institute for Astrophysics. The deposits appear low in density and somewhat transparent, which matches with other discoveries of frozen water on Mars. Indeed, no models "reproduced the properties of the MFF" without involving ice, Cicchetti says, per the BBC's Sky at Night. It's possible the deposits formed when Mars' axial tilt (now 25 degrees) varied from 10 to 60 degrees billions of years ago, per Space.com. With the poles closer to the sun, large quantities of water ice may have formed along the equator before being buried by volcanic ash. (More Mars stories.)