Water discovered on Mars, sort of

Curiosity finds water molecules locked in planet’s soil.

The lines “water, water, everywhere, nor any drop to drink,” from “The Rime of the Ancient Mariner,” may have a new extraterrestrial meaning. On September 26, NASA announced that the Mars Curiosity rover had discovered a surprising amount of water in the planet’s soil. This discovery is being heralded as the rover’s most significant since landing on the Red Planet fourteen months ago, and has new implications for potential human colonization and the existence of life.

Perhaps surprisingly, this isn’t the first discovery of water on Mars. Scientists have known of vast stores of frozen polar water since 2005, when the Mars Reconnaissance Orbiter confirmed their existence. Curiosity sampled soil near Mars’s equator, far enough from the poles for water not to freeze. What makes this discovery unique is its implications for how common water might be on every other part of the planet.

What was perhaps most surprising to Curiosity scientists was the amount of water found, about two per cent of the soil’s weight. Laurie Leshin, co-author of the discovery’s paper, described it as follows: 

“If you took about a cubic foot of the dirt and heated it up, you’d get a couple of pints of water out of that—a couple of water bottles.” 

Of course, Curiosity had to heat the sample to 835° Celsius, but the example remains useful in visualizing the volume present.

Upon NASA releasing the paper outlining the discovery,  scientific media was awash in headlines proclaiming, “water discovered on Mars.” This brings to mind lakes spotted across the barren desert surface, the kind of water you can skip rocks on. But in reality, this discovery is far more subtle. The water discovered in the Martian soil is chemically-bonded to minerals and particulate; it’s not the kind of water you can just pump out of the ground. The soil would certainly not ‘feel’ wet.

What does this discovery tell though, and why has it made such scientific waves?

Firstly, it bolsters the evidence that Mars was once a wet planet, possibly suitable for the formation and existence of life as we know it on Earth. Yet the water discovered would be of little use to any life forms clinging on to existence on the barren planet, as its bonded form couldn’t be directly consumed.

Secondly, it holds implications for potential future visitation and colonization of Mars. The water locked in Mars’s soil, vast volumes if uniform across the planet, could support early explorers, or even colonizers. Yet our understanding of Mars’s near-static water cycle is poor. How much humans could consume and how that might affect the planet’s systems would have to be initially determined.

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