Curiosity used its precision drill, the first instrument of its type sent to another planet, to core two small holes in a particularly interesting looking rock named John Klein. The first drilling was a test run, but the second produced a tablespoon of powder that was fed into the rover's Chemistry and Mineralogy (CheMin) and Sample Analysis at Mars (SAM) instruments for analysis.
Four results were radioed back to ground controllers before a computer glitch suspended science operations last week.
The John Klein rock appears to be shot through with veins of minerals that are deposited by flowing water.
"There's definitely evidence that water has been at work here," said geochemist and Mars exploration planning group chairman David Des Marais, with NASA's Ames Research Center in Moffett Field, Calif.
"The geochemical consequences are yet to be determined," he added.
"One of the of the nice things about this landing site is the low elevation. If there ever was a crater lake on Mars, it should have been in Gale, so I think in that sense we're on to something here," Des Marais said.
With ample evidence of past surface water on Mars, scientists hope to answer a far more taxing questions about organics.
"Organics on Mars should be there even if there is no life from meteorites," geochemist Samuel Kounaves with Tufts University in Medford, Mass., told Discovery News.
Like most scientists Kounaves suspects the surface of Mars is devoid of organics due to radiation and perchlorates, but the question of what lies beyond is only beginning to be answered.
"If you dig inside a rock, or if you dig down far enough, or back in time far enough, there may not have been enough perchlorates or exposure to ultraviolet light to cause these reactions (that destroy organics) so going deep in rocks or deep underground there's a good chance that organics may have survived there," Kounaves said.
"The big puzzle has been are we not finding organics because the instruments can't detect them, or we not finding them because they really aren't there?" he said.
"It's possible Mars 2 billion years ago had less oxidizing properties and organics were surviving and they got buried and they're inside the rock right there waiting for us," Kounaves said.
A press conference to discuss Curiosity's first drill sample results begins at 1 p.m. EDT Tuesday.