Mars Was Mild And Wet Long Ago; Curiosity Rover Analyzes Tell-All Rocks For 10-Year Anniversary (SLIDESHOW)

Rock sample analyses by NASA's Opportunity rover suggested Mars' wet environment was milder and older than researchers had previously believed.

"These rocks are older than any we examined earlier in the mission, and they reveal more favorable conditions for microbial life than any evidence previously examined by investigations with Opportunity," Opportunity Deputy Principal Investigator Ray Arvidson, a professor at Washington University in St. Louis said in a NASA news release.

The findings come just in time for Opportunity's tenth anniversary on the Red Planet. The rover's mission was only supposed to last for three months. Since then it had driven 24 miles from its original landing spot.

The rocks were found along the rim of the Endeavour Crater. A NASA Jet Propulsion Laboratory team used a mineral-mapping instrument on the Reconnaissance Orbiter (MRO) to guide their search for interesting objects.

The rover detected a clay mineral called iron-rich smectite; the team examined the mineral in its "natural context." The team believes the wet conditions that formed the minerals occurred before the formation of the Endeavor Crater, about four billion years ago.

"The more we explore Mars, the more interesting it becomes. These latest findings present yet another kind of gift that just happens to coincide with Opportunity's 10th anniversary on Mars," Michael Meyer, lead scientist for NASA's Mars Exploration Program, said in the news release. "We're finding more places where Mars reveals a warmer and wetter planet in its history. This gives us greater incentive to continue seeking evidence of past life on Mars."

For an older rover Opportunity is still extremely "healthy" and capable of carrying out the researchers' tasks.

"We're looking at the legacy of Opportunity's first decade this week, but there's more good stuff ahead," Steve Squyres of Cornell University, the mission's principal investigator said in the news release. "We are examining a rock right in front of the rover that is unlike anything we've seen before. Mars keeps surprising us, just like in the very first week of the mission."

Rovers have played an important role in Red Planet research over the past decade.

"Over the past decade, Mars rovers have made the Red Planet our workplace, our neighborhood," John Callas, manager of NASA's Mars Exploration Rover Project, said in the news release. "The longevity and the distances driven are remarkable. But even more important are the discoveries that are made and the generation that has been inspired."