On February 13, 2019, NASA officially ended the Mars Exploration Rovers Mission at a press conference at the Jet Propulsion Laboratory in Pasadena California. The rovers Spirit and Opportunity touched down on Mars in January 2004, combined they covered almost 33 miles of Martian ground, took 342,432 photographs, and greatly added to our knowledge of Mars.
Both rovers, but especially Opportunity, provided significant evidence that Mars was very likely warm and wet at points in its history. The “blueberries” found early in the mission were determined to be hematite that formed in acidic groundwater. Later in the mission, and miles away from the landing site at Endurance Crater, clay minerals were found. These minerals would have required water with a pH near 7 (neutral). Not too shabby at all for rovers with an original 90 Martian day (Sol) mission with a goal of driving 3300 feet (about a kilometer).
Opportunity lasted for nearly 60 times the length of the original planned mission and drove nearly 45 times as far as originally planned. It overcame a number of mobility and computer hurdles and earned its reputation as the plucky little rover that could. We learned just as much about how to build and program rovers from Spirit and Opportunity as we did about Mars. Check out some of the awesome stuff NASA has on their website about Opportunity. I think my favorite tribute so far has been the alt text on Randall Munroe’s XKCD: “Thanks for bringing us along.” Thank you, Opportunity, your twin Spirit, and all who worked with you for all the pictures, science, and excitement.