Something big is happening with NASA’s Mars rover Curiosity, but the space agency doesn’t seem ready to announce it just yet. 

NPR recently took a visit to NASA’s Pasadena, Calif., Jet Propulsion Laboratory and apparently found that the spacecraft has made a potentially earth (or Mars)-shattering discovery, which the agency says is not yet ready to be publicly discussed.

Curiosity contains an instrument called SAM, which is able to analyze the chemical makeup of nearly any object placed into it. SAM can analyze soil, rocks and even air on Mars, determining exactly what the substance is made of. And SAM has NASA officials brimming with excitement.

"We're getting data from SAM as we sit here and speak, and the data looks really interesting," John Grotzinger, the principal investigator for the rover mission, told NPR. "The science team is busily chewing away on it as it comes down.”

"This data is gonna be one for the history books. It's looking really good," he said, cryptically.

But as excited as NASA and Grotzinger are by the data coming in from Curiosity, the space agency says it will be several weeks before it can announce what it has, well, unearthed.

Why isn’t NASA ready to make the purportedly historic announcement? According to Grotzinger, it’s because the team can’t take any chances with publishing anything in error.

The problem is, a few weeks ago, scientists on the Curiosity project believed they had found methane in the Martian atmosphere. Much of Earth’s supply of methane in the air is produced by animals and plants, and if Mars did indeed contain methane, it could mean hope for life on the Red Planet.

But the team was cautious about publishing the results, because the air samples could have been contaminated.

"We knew from the very beginning that we had this risk of having brought air from Florida. And we needed to diminish it and then make the measurement again," he says. 

Grotzinger’s suspicions turned out to be entirely correct. Another analysis of Martian air turned up no traces of methane. So it’s entirely understandable that NASA would want to avoid publishing its newest discovery until it's 100 percent sure of what it has found.

Curiosity hasn't given up on looking for methane on the surface of Mars either.

“SAM will continue to search for methane, to determine if methane does vary with time,” NASA scientist Sushil Atreya said at a press briefing earlier in November. “So stay tuned; the story of methane has just begun.”