Opportunity
Opportunity was a NASA Mars rover, part of the Mars Exploration Rover mission, that landed in Meridiani Planum on January 25, 2004. Originally designed for a 90‑sol mission, it operated for nearly 15 years—more than 5,000 sols—traversing over 45 km and providing strong evidence that Mars once held liquid water. It ceased communications after a global dust storm in June 2018 and was declared complete in February 2019.
Source: science.nasa.gov
APODs including "Opportunity"
Humphrey Rock Indicates Ancient Martian Water
10/03/2004
How prevalent was water on Mars? Results from the Spirit rover now indicate that Gusev crater likely had a wet past, a result that comes shortly after Spirit's twin rover Opportunity uncovered clear evidence of past water at Meridiani Planum on the other side of Mars. Evidence uncovered by Spirit and released last week focussed on a large rock of unusual shape nicknamed Humphrey, shown above near the image bottom. Detailed inspection of the rock revealed a bright material filling internal cracks. Such material may have crystallized from water trickling through the volcanic rock. The amount of Mars once covered by ancient water remains unknown, as both rovers landed in regions thought likely to once be underwater. Spirit continues to roll across Mars, recently passing the 300-meter mark on its way to Bonneville crater.