Locked away beneath the surface of Mars are vast quantities of water ice. But the properties of that ice–how pure it is, how deep it goes, what shape it takes–remain a mystery to planetary geologists. Those things matter to mission planners, too: Future visitors to Mars, be they short-term sojourners or long-term settlers, will need to understand the planet’s subsurface ice reserves if they want to mine it for drinking, growing harvests, or converting into hydrogen for fuel.
Trouble is, dirt, rocks, and other surface-level contaminants make it hard to study the stuff. Mars landers can dig or drill into the first few centimeters of the planet’s surface, and radar can give researchers a sense of what lies tens-of-meters below the surface. But the ice content of the geology in between–the first 20 meters or so–is largely uncharacterized.
Fortunately, land erodes. Forget radar and drilling robots: Situate a spot of land laid bare by time, and you have a direct line of sight on Mars’ subterranean layers–and any ice deposited there.
Now, scientists have discovered such a site. In fact, with the help of HiRISE, a powerful camera aboard NASA’s Mars Reconnaissance Orbiter, they’ve saw several.
In this week’s issue of Science, researchers led by USGS planetary geologist Colin Dundas present detailed observations of eight Martian regions where eroding has uncovered big, steep cross-sections of underlying ice. It’s not just the volume of water they found( it’s no mystery that Mars harbors a lot of ice in these particular regions ), it’s how mineable it promises to be. The deposits begin at depths as shallow as one meter and extend upwards of 100 meters into the planet. The researchers don’t calculate the quantity of ice present, but they do note that the amount of ice near the surface is likely more extensive than the few locations where it’s exposed. And what’s more, the ice looks pretty damn pure.