A Delta II rocket lifted off from Cape Canaveral at 03:18:15 EDT. It carried a 384-pound rover named Opportunity, sealed inside a protective aeroshell. The launch was flawless. The mission was a duplicate; its twin, Spirit, had launched three weeks earlier. Their official designation was Mars Exploration Rover B. The goal was simple: land on opposite sides of Mars and look for signs of past water.
Opportunity landed in Meridiani Planum on January 25, 2004. Its first image showed a small crater's rim just 20 feet away. The rover rolled down into Eagle Crater and immediately found bedrock. The bedrock contained gray hematite spherules, nicknamed 'blueberries,' and cross-bedding patterns that could only form in liquid water. The site was not just damp; it had once been the shoreline of a salty sea.
The mission was designed for 90 Martian days. It lasted 5,352. Opportunity drove 28.06 miles, a record for off-Earth travel. It survived dust storms, got stuck in a sand dune for weeks, and eventually lost mobility in one wheel, driving backwards to compensate. The rover's final communication came on June 10, 2018, after a planet-wide dust storm obscured the sun and drained its batteries.
Opportunity’s legacy is geological. It provided conclusive, ground-truth evidence that Mars once had persistent liquid water and conditions potentially suitable for life. The mission shifted the scientific question from whether water existed to where and for how long. The rover’s endurance became a quiet engineering triumph, a machine that outlived its warranty by a factor of sixty.