The Mars Exploration Rover Opportunity was a robotic rover that explored the surface of Mars from 2004 to 2018. It was part of NASA's Mars Exploration Rover mission, designed to search for signs of past water and assess the planet's geology. Opportunity operated for nearly 15 years, far exceeding its original 90-day mission. Opportunity traveled over 28 miles (45 kilometers) across the Martian landscape, discovering various geological features and providing valuable data about the planet's history. Its findings contributed significantly to our understanding of Mars and helped pave the way for future exploration missions.