Space: Opportunity (Mars Exploration Rover)

American robotic rover that was active on Mars from 2004 until 2018. The rover, called Opportunity, and also known as MER-B (Mars Exploration Rover – B) or MER-1, was launched on 7 July 2003 and landed on Mars' Meridiani Planum on 25 January 2004 at 05:05 Ground UTC (about 13:15 Mars local time), three weeks after its twin Spirit (MER-A), also part of NASA's Mars Exploration Rover Mission, touched down on the other side of the planet.

With a planned 90 sol (Martian days) duration of activity, Spirit functioned until getting stuck in 2009 and ceased communications in 2010, while Opportunity was able to stay operational for 5111 sols after landing, maintaining its power and key systems through continual recharging of its batteries using solar power, and hibernating during events such as dust storms to save power. This careful operation allowed Opportunity to operate for 57 times its designed lifespan, exceeding the initial plan by 14 years, 47 days (in Earth time).

On 28 July 2014, NASA announced that Opportunity, after having travelled over 40 km (25 mi) on the planet Mars, has set a new "off-world" record as the rover having driven the greatest distance, surpassing the previous record held by the Soviet Union's Lunokhod 2 rover that had travelled 39 km (24 mi) on the Moon.

Last contact with the rover was on 10 June 2018. The mission was declared ended on 13 February 2019.