It has been written many times in these pages, and it begs repeating: this rover was sent on a 90-day expedition, with the mission success mobility objective of driving 600 meters. In March, Opportunity completed 42.195 kilometers or 26.2 miles. It’s the first marathon “run” on another planet. And in April – the 4000th sol. “This rover just keeps giving and giving,” said Planetary Society President Jim Bell, professor of astronomy and planetary scientist at Arizona State University and lead scientist on the MERs’ panoramic cameras (Pancams).

Source: Mars Exploration Rovers Update: Opportunity Logs Sol 4000, Digs Spirit of St. Louis Crater | The Planetary Society