So, what is NASA Curiosity's history-changing discovery?

NASA/AP

John Grotzinger, the principal investigator for the mission, said his team has found something really cool.

NASA's Curiosity rover has another, even bigger, apparently history-making discovery that might just change everything about the universe as we know it — but they aren't telling anyone what it is, exactly, until scientists can be absolutely sure it's not a dud. Thanksgiving nerd speculation, of course, is go for launch.

John Grotzinger, the principal investigator for the mission, tells NPR's Joe Palca in an interview that aired today that his team has found something really, really cool on Mars with Curiosity's SAM soil-collecting device: "This data is gonna be one for the history books. It's looking really good," Grotzinger exclaimed. Unfortunately, NASA won't be telling us what said cool secret is until they run a bunch of tests to make sure what they found is authentic. 

The scientists thought they had made an exciting breakthrough earlier, when a tool picked up some methane in the Mars atmosphere, which would have been a first — and could indicate that life previously existed on Mars. They had to test to make sure the methane didn't travel with the Rover from earth, though, and once they did their due diligence it turned out the methane piggy-backed from earth. The team was predictably deflated. 

Read more at The Atlantic Wire