Huge Water Reserves Found All Over Mars

New NASA images show layers of ice peeking out of eroded cliffs—a potential boon for future humans on the red planet.

Eroded banks throughout Mars's mid-latitudes reveal underground bands of bluish material. Spectra of these layers—which start three to six feet beneath the surface—strongly suggest that they are made of water ice.

At sites across the midsection of Mars, scientists have found layers of water ice buried mere feet beneath the red planet’s surface. The discovery adds crucial detail to Mars’s geologic history, and it may shape how future humans on Mars get their water.

"This is a new window into ground ice on Mars," says Colin Dundas, the U.S. Geological Survey geologist who co-discovered the ice layers.

Scientists have long theorized that reserves of water ice are locked underground on Mars. In 2002, the NASA Odyssey mission scanned the planet from orbit and detected signs of shallow ground ice at high latitudes. In 2008, the NASA Phoenix mission dug up water ice at its landing site near the Martian north pole.

Mars 101

And in late 2016, scientists using the Mars Reconnaissance Orbiter (MRO) found a buried ice sheetat Mars’s mid-latitudes that holds about as much water as Lake Superior. But until Dundas’s study, published today in Science, scientists struggled to understand the extent and accessibility of Mars’s subsurface ice layers.

The eight sites featured in the new study include steep banks where, much like cutting into a cake, erosion has exposed layers of rock and ice that MRO could see from overhead. The bands of ice first appear between three and six feet underground, supporting the notion that Mars’s mid-latitudes periodically saw large snowfalls millions of years ago, when Mars was tilted on its axis at a steeper angle than it is today, says Dundas.

Gullies fringe the edge of southern Mars's Hale crater. On Earth, these structures usually form through the action of liquid water.

In 2004, the NASA Mars rover Opportunity found sphere-like grains nicknamed "blueberries." These grains of hematite probably formed in wet sediments.

Alluvial fans are gently sloping wedges of sediments laid down by flowing water. Some of the best-preserved alluvial fans on Mars are in Saheki Crater, seen here.

In 2015, scientists found dark streaks flowing down some Martian hillsides. Initially, salty liquid water was considered the culprit, but recent studies suggest that the streaks are in fact dry cascades of dust.

In October 2017, scientists unveiled evidence that 3.7 billion years ago, Mars's Eridania basin was a vast ocean with hydrothermal vents—potentially offering conditions friendly to ancient life.

Gullies snake down the northwest rim of Hale crater. It's unclear how the gullies formed, but some resemble features on Earth that are carved by flowing water.

In 2012, NASA's Curiosity rover found the remains of a stream that once ran vigorously across Mars's surface. These rocks, which contain ancient streambed gravels, were the first of their kind found on Mars.

The pinkish, scaly texture is Martian bedrock that water altered long ago, forming clay-bearing rocks. It's still unclear how exactly the rock and water interacted.

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"[They are] very cool images that capture the subsurface ice predicted by theory," says Caltech planetary scientist Bethany Ehlmann, who wasn’t involved with the study. "Also, we may be able to core the ice for a record of climate change on recent Mars, much like we do on Earth."

The discovery could also influence how future astronauts—who may one day land in Mars’s mid-latitudes—slake their thirst.

Human missions to Mars would likely rely on extracting water from the local environment, either baking it out of hydrated minerals or mining it from ice deposits. Humans would then drink the water or break it down into hydrogen and oxygen, which could then be used to make breathable air and methane for rocket fuel.

As a 2016 NASA study makes clear, ice may yield more water per scoop than minerals, but if accessing this ice requires digging through 30 feet of rock, then ice mining ends up being too inefficient. That picture changes, however, if ice sheets lie within only a few feet of the surface.

"It’s looking more encouraging that water ice could be available at depths shallow enough that could be used as resources for human missions to Mars," says Angel Abbud-Madrid, the director of the Center for Space Resources at the Colorado School of Mines.

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