Sheets of ice, running 300 feet deep in some cases, have been exposed just below the surface of Mars, according to a new paper published Friday in Science.
Some locations on Mars are known to have water ice just below the surface, but how much has remained unclear. Dundas et al. used data from two orbiting spacecraft to examine eight locations where erosion has occurred. This revealed cliffs composed mostly of water ice, which is slowly sublimating as it is exposed to the atmosphere. The ice sheets extend from just below the surface to a depth of 100 meters or more and appear to contain distinct layers, which could preserve a record of Mars' past climate. They might even be a useful source of water for future human exploration of the red planet.
Most of the water that’s been discovered or detected on Mars is unable to be fully characterized, as it is covered by Martian land, dust, and rock. But as WIRED reports, the findings are incredibly exciting not because they’ve found the water but because for the first time, they feel closer to being able to determine the quality, quantity, and makeup of some of the water that is closer to the surface. This is due to higher resolution photography and the natural land erosion on the planet.
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 found several.
In this week's issue of Science, researchers led by USGS planetary geologist Colin Dundas present detailed observations of eight Martian regions where erosion has uncovered large, 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 estimate 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.
The researchers theorize that the ice they are seeing may have considerably less debris, and the quantity of that ice seems to be much larger than previously thought.
"On Mars, when you see something bright, it usually means ice,” says Richard Zurek, chief scientist for the Mars Program Office at NASA's Jet Propulsion Laboratory, who was unaffiliated with the study. Most of the material on Mars reflects little light, "but the albedo readings on these exposed sections show that this is very bright stuff," he says. "And the spectrometer readings support that this is water ice and not ice-cemented soil, which would be much harder to convert into water as a resource."
But this is not the only reason it might be easier to extract essential resources for future Mars visitors.
Researchers previously used MRO's Shallow Radar (SHARAD) to map extensive underground water-ice sheets in middle latitudes of Mars and estimate that the top of the ice is less than about 10 yards beneath the ground surface. How much less? The radar method did not have sufficient resolution to say. The new ice-scarp studies confirm indications from fresh-crater and neutron-spectrometer observations that a layer rich in water ice begins within just one or two yards of the surface in some areas.
You and I can dig one or two yards underground. And as with all scientific discoveries, the import is not simply what we could take from Mars, but what we could learn about Mars’ history.
"If you had a mission at one of these sites, sampling the layers going down the scarp, you could get a detailed climate history of Mars," suggested MRO Deputy Project Scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory, Pasadena, California. "It's part of the whole story of what happens to water on Mars over time: Where does it go? When does ice accumulate? When does it recede?"
Amazing.