Curiosity didn't find the Martian rock known by researchers as "Black Beauty" or, formally, NWA 7034. A meteorite, it was actually discovered in the Sahara desert in 2011. It's hardly the first meteorite discovered on Earth having originated on Mars (there are 110 others), but it's strikingly different in one way: it has about 10 times the water as other Martian meteorites. This information comes courtesy of a year of intense research on the rock by NASA-funded astrobiologists and cosmochemists. Their work is out today in Science.
Black Beauty is among the oldest of Martian meteorites studied, originating during the beginning of the planet's current geologic period, the Amazonian. This is crucial because it means that for the very first time we have a piece of Mars captured during one of the planet's major periods of evolution. It's a piece of Mars, but of a very different Mars than the one we currently know based on its meteorite siblings. It's actually quite a bit closer in nature to current lander-based analysis of Mars' composition, which is good news for Curiosity.
"The contents of this meteorite may challenge many long held notions about Martian geology," says NASA's John Grunsfeld. "These findings also present an important reference frame for the Curiosity rover as it searches for reduced organics in the minerals exposed in the bedrock of Gale Crater." It's not wet by any means; the water concentration is still extremely tiny by the standards of most life on Earth.
As a bonus, the rock also boasts an unexpected concentration of oxygen isotopes, suggesting the planet has (or had billion years ago) reservoirs of oxygen distributed within its crust. It is, in the researchers' words, "the most geochemically enriched rock from Mars that has been found to date."
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