NASA's Curiosity rover completed one Martian year, 687 Earth days, on June 24, 2014. By then it had met the mission's main goal. Two mudstone samples drilled at Yellowknife Bay in Gale Crater showed the site was once a lakebed with mild water, the key chemical ingredients for life, and a chemical energy source used by some microbes on Earth.
Curiosity also measured radiation during the flight and on the surface, found evidence that much of Mars' early atmosphere was lost from the top, detected little if any methane, and made the first age determination of a rock on Mars.
via NASA’s Mars Curiosity Rover Marks First Martian Year with Mission Successes | NASA