Curiosity rover successfully drilled into a Martian rock, giving us a peek at the Red Planet's habitable history. The 1.8-inch-wide scoop of powdered rock revealed that ancient Mars could have supported living microbes.

"We have found a habitable environment that is so benign and supportive of life that, if this water had been around and you had been on the planet, you would have been able to drink it," said John Grotzinger, Curiosity project scientist.

After breaking down and analyzing the powder, scientists found the rock contained sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon — all key chemical ingredients for life.

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"I think this is probably the only definitively habitable environment [outside of Earth] that we have described and recorded," said David Blake, principal investigator for Curiosity's CheMin instrument.

The rock, dubbed "John Klein," is located in an area called Yellowknife Bay, a very low point of the Gale Crater that scientists have described as a "time-capsule of evidence." Made up of sedimentary rocks with different textures, the area signals a geologically active planet with a very wet history.

"Clay minerals make up at least 20% of the composition of this sample," said Blake. That type of material is a product of the reaction of relatively fresh water.

The John Klein rock and its neighbors are a far cry from what scientists saw in 2004 from Opportunity rover, which was parked in a different area of Mars called Endurance Crater. Opportunity determined the rocks in that area were formed from sulfate-rich sandstone, signaling a very acidic ancient aqueous environment that was not habitable.

However, scientists say Curiosity's location deep in the Gale Crater presents a different story. As lead scientist Michael Meyer put it, Yellowknife Bay is chapter one of Mars' autobiography.

"We have characterized a very ancient, but strangely new 'gray Mars' where conditions once were favorable for life," says Grotzinger.

You can see the difference in the two areas in the composite image below. The photo on the left is "Wopmay" rock in Endurance Crater, taken by Opportunity's panoramic camera in 2004; the image on the right from Curiosity's Mast Camera is of rocks from "Sheepbed" unit in Yellowknife Bay in Gale Crater.

Before this drill, Mars Science Laboratory scientists were careful to not over-promise Curiosity's mission.

"When you land on Mars, strange things can happen," says Grotzinger. "I think the positive message here is that we're getting better at this, and this is not by accident [...] You always need to be careful when you're working on Mars."

In November 2012, NPR quoted Grotzinger as saying "this data is gonna be one for the history books." The interview sparked rumors that Curiosity had found something "earth-shaking" on Mars. However, as Mashable first reported, the statement was taken out of context, and NASA was forced to backtrack to clarify the situation.

When asked Tuesday if Grotzinger had actually known during that infamous NPR interview that these latest results were a possibility, he shook his head laughing and denied any firm knowledge. "I feel better about it now," he said with relief.

Images courtesy of NASA/JPL