NASA Curiosity Rover Finds New Evidence That Ancient Mars Was Habitable

The pale rock in the upper center of this image, about the size of a human forearm, includes a target called "Esperance," which was inspected by NASA's Mars Exploration Rover Opportunity.

This image is a composite of three exposures taken by Opportunity's panoramic camera during the 3,262nd Martian day, or sol, of the rover's work on Mars (March 28, 2013).

CREDIT: NASA/JPL-Caltech/Cornell/Arizona State Univ.

NASA's Mars rover Opportunity has made perhaps the biggest discovery of its nearly 10-year career, finding evidence that life may have been able to get a foothold on the Red Planet long ago.

The Opportunity rover spotted clay minerals in an ancient rock on the rim of Mars' Endeavour Crater, suggesting that benign, neutral-pH water once flowed through the area, scientists said.

"This is water you could drink," Opportunity principal investigator Steve Squyres of Cornell University told reporters today (June 7), explaining why the rock, dubbed "Esperance," stands out from other water-soaked stones the rover has studied.

"This is water that was probably much more favorable in its chemistry, in its pH, in its level of acidity, for things like prebiotic chemistry — the kind of chemistry that could lead to the origin of life," Squyres added.