On January 25, 2004, the Opportunity rover landed on Mars for a mission that was going to last 90 sols (90 Martian days, which are a bit longer than Earth days). Ten years later, she's still going strong and adding to our knowledge of the red planet.
Sadly, her twin sister Spirit got caught in a sand trap in 2009 and made her final transmission in 2010 as winter began on Mars. She didn't survive the winter and finally, in 2011 NASA formally ended her mission. You can read
Spirit's story here.
