These might be the best places for future Mars colonists to look for ice

If we ever start an extraterrestrial colony on Mars, we'll need water for a host of essential services, and most obviously for something to drink.

But while there's plenty of water ice at the planet's poles, the elevation is too high and there's limited access to sunlight for power. So we'll want to look for ice we can dig out from under the surface at lower latitudes. A new study published in Nature Astronomy suggests a couple of locations that might work particularly well.

The locations come from the Mars Subsurface Water Ice Mapping (SWIM) project, which analyzes historical mission data taken over 20 years of Mars missions. The project looks at five different remote sensing datasets collected by the Mars Odyssey orbiter, Mars Reconnaissance Orbiter, and Mars Global Surveyor.

Each of our five techniques looks at a sort of different proxy or a different way of trying to find signatures of water ice," says Gareth Morgan, a researcher with the Planetary Science Institute in Tucson, Arizona, and the lead author of the new study. These techniques include thermal and geomorphic mapping that looks for geological surface changes caused by ice that lies less than five meters below the surface.

Morgan and his team found a few locations that would seem to work perfectly in the northern hemisphere, namely the flat Arcadia Planitia lowlands in the mid-to-upper latitudes, and the glacial networks across Deuteronilus Mensae farther east and slightly to the south. The former is an ancient region of old volcanic flows, with a suspected history of massive snowfall from tens of millions of years ago. The new results would seem to suggest those deposits slowly moved underground into very shallow depths that might be easy to drill into.

Arcadia Planitia and Deuteronilus Mensae are both located within the northern hemisphere of Mars, in mid-range altitudes. USGS

Meanwhile, Deuteronilus Mensae is home to modern-day glaciers, and exists between cratered highlands to the south and low plains to the north. The ice here is effectively the remnants of what were probably more extensive glacial structures in the past. It should be located under either a thin two-meter covering of Martian soil and rock or a very porous material that's a few meters thick. In either instance, the ice there would be pretty accessible to Mars colonists.

NASA funded this first round of analysis only to concentrate on Mars's northern hemisphere. Morgan believes that's because there are large plains in the region that would make it easier to land a spacecraft on the surface. But he would love to follow up on a deeper analysis of subsurface ice deposits in the southern hemisphere as well.

Making this work open to the community capitalizes on all available expertise, both inside and outside NASA," says Leslie Gertsch, a geological engineer at Missouri University of Science and Technology, who was not involved with the study. The next step is to equip future missions with better ice-mapping capability-0.5 to 15 meters below the surface, a depth range that could be accessed by remote mining techniques."

NASA's already in the process of prospecting for water ice on the moon. Considering how difficult it is to go to Mars (the launch window is once every two years), it's worth thinking about these issues much earlier.

The scarcity of sufficiently detailed subsurface data, even on Earth, is why mining is always a gamble," says Gertsch. Yet it is a necessary one for humanity to survive elsewhere."