NASA MER-B · Mission Complete (2004–2018)
The greatest overachiever in the history of space exploration. Designed to last 90 days and drive 600 metres, Opportunity instead explored Mars for 14 years and 138 days, covered a full marathon distance of 45.16 km, and fundamentally changed our understanding of Mars's watery past. From the moment its airbags bounced to a stop inside Eagle Crater on 25 January 2004, Opportunity delivered discovery after discovery.
5,352 sols (14 years, 138 days). Designed for just 90 sols. Exceeded design life by 55×.
45.16 km — a full marathon. The farthest any wheeled vehicle has traveled off Earth. Set the record on 27 March 2015.
Eagle Crater, Meridiani Planum (1.95°S, 354.47°E). Selected for orbital detection of grey hematite — a mineral that typically forms in water.
185 kg. Solar-powered with twin panels. Dust accumulation was periodically cleared by wind events ("cleaning events") that extended its life for years.
Panoramic Camera (Pancam), Miniature Thermal Emission Spectrometer (Mini-TES), Alpha Particle X-ray Spectrometer, Mössbauer Spectrometer, Microscopic Imager, Rock Abrasion Tool.
US$400 million (combined MER programme with Spirit). Launched on a Delta II 7925H from Cape Canaveral on 8 July 2003.
Within weeks of landing, Opportunity found tiny iron-rich spherules embedded in bedrock — nicknamed "blueberries." These hematite concretions form in water-saturated rock, providing the first ground-truth evidence that liquid water once existed on the Martian surface.
At Burns Cliff in Endurance Crater, Opportunity photographed cross-bedded sandstone layers — a geological structure created by flowing water. The pattern indicated shallow, wind-rippled water that intermittently covered the region billions of years ago.
After driving 21 km over three years, Opportunity reached the 22 km-wide Endeavour Crater in 2011. At its rim, the rover discovered clay minerals (smectites) indicating ancient water with near-neutral pH — far more hospitable to life than the acidic conditions found earlier. These rocks predated everything else Opportunity had studied.
In 2017, Opportunity began exploring Perseverance Valley, a channel carved into Endeavour's rim, investigating whether water or wind created it. In June 2018, a planet-encircling dust storm plunged the sky into darkness. Solar power dropped to zero. After 835 recovery attempts over eight months, NASA declared the mission complete on 13 February 2019.