NASA’s Opportunity rover landed on Mars on January of 2004, and this week, it set a new off-Earth roving distance record, accruing just over 40 kilometers (25 miles) of driving. 

“Opportunity has driven farther than any other wheeled vehicle on another world," John Callas of NASA's Jet Propulsion Laboratory says in a news release. "This is so remarkable considering Opportunity was intended to drive about one kilometer and was never designed for distance.”

Long before Curiosity arrived on the scene, the rover pair Spirit and Opportunity were cruising on the Red Planet. They were each designed to operate for just 90 sols (or Martian days, about 24 hours and 39.5 minutes long), Ars Technica explains, and they both exceeded that lifespan. Spirit’s solar power arrays stopped generating electricity in 2010, and Opportunity is still chugging along after celebrating its 10th anniversary. In this time, this plucky rover has been helping us understand the composition of Mars, even sending back clues of past water activity. 

“No one in their wildest dreams thought the rover would last this long,” Callas tells the Los Angeles Times. “People made bets early on -- ‘Maybe we can get to the first Martian winter,’ ‘Maybe we can get two years out of it’ -- but no one thought that it would last this long.”

Driving just 48 meters (157 feet) on July 27, 2014 put Opportunity's total odometry at 40.25 kilometers (25.01 miles). Its route is mapped above. This month's driving brought the rover southward along the western rim of Endeavour Crater; it arrived at this 22-kilometer (14-mile) wide crater in 2011. These sites show evidence of ancient environments with less acidic water than those examined at the rover’s landing site, inside the Eagle Crater.  

The previous distance record was held by the Soviet Lunokhod 2 rover, which landed on Earth's moon on January 15, 1973. There, it drove about 39 kilometers (24.2 miles) in less than five months. As Opportunity neared this driving record earlier this year, the rover team chose the name Lunokhod 2 for a crater about 6 meters (20 feet) in diameter on the outer slope of the western rim of Endeavour Crater. Pictured to the right is a natural color view from Opportunity showing the Lunokhod 2 Crater, which lies south of Solander Point. It was obtained during Opportunity’s 3,644th sol of exploration (that is, April 24 of this year). Part of the rover, including its solar arrays and panoramic camera, is visible at the bottom. 

If Opportunity can continue to operate the distance of a marathon -- about 42.2 kilometers (26.2 miles) -- it will approach the next major investigation site mission, which has already been dubbed "Marathon Valley." Observations from spacecraft orbiting Mars suggest several clay minerals are exposed close together at this valley, which is surrounded by steep slopes of visibly different layers.

This chart below provides a comparison of the distances driven by various wheeled vehicles on the surfaces of Mars and our moon as of July 28, 2014. Here, it’s been cropped to fit the top three, though the full image (which includes Curiosity) is available here. 

Images: NASA/JPL-Caltech/MSSS/NMMNHS (top), NASA/JPL-Caltech/Cornell/Arizona State Univ. (middle), NASA/JPL-Caltech (bottom)