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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