A "selfie" of that NASA's Curiosity Mars rover. (NASA/JPL-Caltech/MSSS)

The Mars Curiosity Rover has found evidence of nitrates, compounds vital to supporting life as we know it. Scientists already knew that Mars had nitrogen gas in its atmosphere, but in order to be used in the chemical processes that keep living things alive it must be "fixed" — the two tightly fused nitrogen atoms that make a molecule of gas must be separated from each other. Without that fixing, most organisms can't access the element. And it's absolutely vital, because it's a building block of DNA and RNA.

In two studies published Monday in the Proceedings of the National Academy of Sciences, researchers report that Mars does indeed have fixed nitrogen. What they actually found was nitric oxide, but the researchers believe this likely came from heated nitrates. That adds weight to the notion that the red planet may once have harbored life, back when it was home to a deep and vast ocean.

[New NASA research says Mars once had a large ocean]

“People want to follow the carbon, but in many ways nitrogen is just as important a nutrient for life,” Jennifer Stern, a planetary geochemist at NASA Goddard Space Flight Center, told the Los Angeles Times. “Life runs on nitrogen as much as it runs on carbon.”

There's no life on Mars today (probably not even any punky little microbes left kicking about) but it's possible that the nitrates came from ancient living organisms. Some creatures are able to fix nitrogen from the atmosphere — that's how Earth gets most of its fixed nitrogen.

The new measurements aren't precise enough to know whether this nitrogen was fixed recently or in the distant past, but researchers could eventually answer that question by comparing the found, fixed nitrogen with the stuff present in Mars's current atmosphere.

[Curiosity readings point to mysterious, pulsing source of methane on Mars]

But whether the nitrates are new or old, they probably came from non-biological processes. On Earth, nitrogen can be "fixed" by lightning strikes, for example. On Mars, they might have come from asteroid impacts.

"Scientists have long thought that nitrates would be produced on Mars from the energy released in meteorite impacts, and the amounts we found agree well with estimates from this process," Stern said in a statement.

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