After 10 years sent roaming Mars, NASA's Opportunity rover found on one side of the Red Planet what Curiosity did on the other: evidence of life-sustaining water.

According to the Los Angeles Times, Opportunity's discovery further solidifies Curiosity's groundbreaking find last year. Lead scientists for the Mars Exploration Rover program Steve Squyers, a planetary scientist at Cornell University, said there is now evidence of life-sustaining water on either side of the Red Planet.

"These are some of the oldest rocks we've looked at - probably the oldest rocks that we've looked at with Opportunity," Squyres told the LAT.

Opportunity landed on Mars in 2004 with its twin Spirit, no longer in commission, and they found signs that pointed to acidic water unfriendly to life of any kind. The new clay mineral discovery of neutral-pH water is believed to be from early on in Mars' history, whereas the acidic water likely came later. The rocks rich in clay may have resembled the those rich in sulfate, but they were also from completely different times.

Lead author of a study published in Science Raymond Arvidson, of Washington University, told Time the "ghost rock" at the center of the discovery was actually a complete surprise.

"When you combine it with the recent results from Curiosity," he said, "it tells you that relatively benign conditions once existed for extended periods in different parts of Mars."

Curiosity is currently en route to Mount Sharp, the centerpiece to the Gale Crater, the rover's landing spot, which Arivdson and other experts believe will be a gold mine for evidence to Mars' history.

"This is way beyond saying we have water on Mars," he told Bloomberg News. "This is trying to get to past chemical conditions of the water, and say something about habitability, and directing future missions to the juiciest havens."