NASA's Opportunity rover may have landed on Mars 10 years ago, but it's still sending valuable data to scientists on Earth. The rover's latest findings show that water once stirred rocks on the edge of the Endeavor Crater — and it was suitable for life.
Much of the evidence of water we've previously seen on Mars shows that it was very acidic — scientists often compare it to Spain's Rio Tinto, which is famous for its deep reddish color and acidity — and therefore not the greatest place to sustain even the "hardiest extremophile microorganisms," as researchers put it. That super-salty, highly-acidic water is a signature trait of a more recent Mars.
See also: 1 Year on Mars: Relive Curiosity's Biggest Moments
However, Opportunity's latest sample was taken from an area that formed more than 3.7 billion years ago, when Mars was still a young planet. The fact that these older rocks show milder conditions bodes well for the theory that the Red Planet could have very well been a favorable place for life or prebiotic chemistry.
"Opportunity's results are significant because they show that on a completely different place on Mars, at a very different point in time," Chief Scientist John Grotzinger told Mashable. "A trend is emerging which shows early Mars was certainly more habitable than it is today, and for an extended period of time that could have lasted hundreds of millions of years."

NASA's Mars Exploration Rover Opportunity recorded the component images for this self-portrait on Jan. 3, 2014 through Jan. 6, 2014, a few days after winds removed some of the dust that had been accumulating on the rover's solar panels.
Image: NASA
These latest results will appear in the Jan. 24 issue of the journal Science.
Opportunity's findings echo what we've already seen from Curiosity rover, which found an ancient streambed where water once flowed in 2012. Last spring, Curiosity drilled into a Martian rock, analyzed a 1.8-inch-wide scoop of powdered rock and confirmed that the planet was once suitable for life.
NASA's Opportunity rover landed on Mars in 2014 and was initially slated for a 90-day mission. Ten years and 24.07 miles later (that's pretty far for a slow-moving rover), it's still fully operational and conducting science experiments on the Red Planet.