Opportunity, also known as MER-B (Mars Exploration Rover – B) or MER-1, is a robotic rover active on Mars since 2004.Launched on July 7, 2003 as part of NASA's Mars Exploration Rover program, it landed in Meridiani Planum on January 25, 2004, three weeks after its twin Spirit (MER-A) touched down on the other side of the planet.With a planned 90 sol duration of activity (slightly more than 90 earth days), Spirit functioned until getting stuck in 2009 and ceased communications in 2010, while Opportunity remains active as of June 3, 2018, having exceeded its operating plan by 14 years, 38 days (in Earth time). Opportunityhas continued to move, make scientific observations, and report back to Earth for over 55 times its designed lifespan. As of January 23, 2018, the rover had traveled 45.09 kilometers (28.02 miles).
Mission highlights include the initial 90 sol mission, finding extramartian meteorites such as Heat Shield Rock (Meridiani Planum meteorite), and over two years studying Victoria crater. The rover survived dust-storms and in 2011 reached Endeavour crater, which has been described as a "second landing site".
