Where’s the Water on Mars? Everywhere!

Scientists have published their first findings from the Curiosity rover’s soil tests, and there’s mixed news for future explorers

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NASA / JPL-Caltech / Malin Space Science Systems

This view shows the patch of veined, flat-lying rock selected as the first drilling site for NASA's Mars rover Curiosity on Jan. 10, 2013

Laurie Leshin fell in love with Mars when she was 10 years old. It was 1976, the year NASA landed its twin Viking probes on the surface of the Red Planet, beaming back the first closeups of the rocky, rust-colored surface of Earth’s nearest neighbor. “They put the Viking mission on the cover of TIME,” she recalls. From that point on she knew she wanted to study Mars.

The dreams of a 10-year-old usually fade, but not this one’s. Leshin, now a planetary geologist and dean of science at Rensselaer Polytechnic Institute, is the lead author of a paper in the latest issue of Science analyzing data beamed to Earth from experiments on the first scoop of Martian soil dug up by the Curiosity rover. “If you’re an astronaut walking around on Mars someday,” she says, “you really want to know what’s in the dirt under your feet, and this is the first detailed look we’ve ever had.”

What jumps out of the analysis right away is that the soil — mostly sandy grains dug from a mound in a spot known as Rocknest, inside of Gale Crater — is the presence of water, which adds up to about 2% of the soil, by weight. “If you took a cubic foot of this material and heated it,” says Leshin, “you’d about get two pints of water. I think that’s pretty amazing.”

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The amazing part isn’t so much that there’s water on Mars; scientists have known for years that the life-giving liquid flowed freely and abundantly across the Martian surface billions of years ago, and that water in the form of ice still exists in reasonable quantities at the planet’s poles. But these sandy particles were blown here from all over Mars before settling to the ground. This one sample, therefore, tells us that the water Leshin’s team found is spread pretty much everywhere on the planet. No matter where astronauts eventually land, they’ll be able to cook their water supplies right out of the dirt.

It’s natural to assume this water is left over from the H2O that was abundant in Mars’ early days (including inside Gale Crater itself), but chemical analysis with Curiosity’s Sample Analysis at Mars instrument says otherwise: a significant amount of the hydrogen in this case isn’t the ordinary variety, but rather a heavy form of hydrogen known as deuterium — and the relative amounts of hydrogen and deuterium in the soil water match those in the tiny bits of water in Mars’ atmosphere. “We think the soil is acting as a sponge,” says Leshin, “pulling in water as it blows around the planet.”

What Leshin’s team didn’t find was any evidence of organic molecules that could hint at life — or rather, she says, “we did detect a few molecules’ worth, but it looks like they were formed in our experiment.” This doesn’t rule out their existence, however. “The soil really isn’t a good place to look for organics,” says Leshin. “Rocks are better. That’s why we brought a drill.” This experiment, which took a half a baby aspirin’s worth of soil, heated it to 1,500°F and analyzed the vapors that emerged, did detect carbon dioxide, oxygen and sulfur compounds that are clearly native to Mars.

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It also found compounds called perchlorates, and that, says Leshin, makes the results a bit of a good news–bad news story for future astronauts. The water is good, but perchlorates are toxic: astronauts who inadvertently breathe in Mars dust could damage their thyroids.

Important as this bounty of new information is to scientists’ growing understanding of Mars’ geological past and present, it comes from just one of five papers published simultaneously in Science that go into greater detail about the kinds of minerals found in the Rocknest scoop, and in a rock known as Jake Matijevic. (It was named after a NASA engineer who helped design Curiosity and other Mars rovers.)

Much of what’s in these other papers is information only a geologist could get excited about, but this is just the first shot in what’s likely to be a volley of discoveries. The drill Leshin refers to has augured its way into several rocks now, and those samples are currently being analyzed. “We have a whole set of papers now in review,” says David Blake, a scientist with the NASA Ames Research Center, who is in charge of Curiosity’s Chemistry and Mineralogy instrument, which uses X-rays to analyze a mineral’s molecular structure. “We can’t really talk about those results yet.”

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Meanwhile, Curiosity is en route to Gale Crater’s central feature, a hill known as Mount Sharp, whose wind-eroded sides have exposed layers that scientists think formed as sediments sank to the bottom of what was a water-filled basin eons ago. If any place can lay bare the story of Mars as it existed billions of years ago, when conditions might have given rise to life, this is it.

Leshin can’t wait for future results — but she also has to admit that her memory of that long-ago inspiration isn’t quite the way it happened. “It turns out,” she says, “that TIME never did put Viking on the cover.” The Viking story appeared inside the magazine; the cover subject that week was gymnast Nadia Comaneci, who stole the show at the Montreal Olympics.

“That must have been why I picked up the magazine in the first place” says Leshin. But once she got to the Viking story, there was no going back.

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