When it comes to out-of-this-world mileage figures, no vehicle can compete with Mars rover Opportunity.
The rover's odometer has reached 25.01 miles after a decade on Mars, marking an off-Earth distance record. The rover traveled about 160 feet over the weekend, enough to break the old record held by the Soviet Union's Lunokhod 2 rover.
Lunokhod 2 rover landed on Earth's moon in 1973 and drove 24.2 miles. That journey took just about five months.
Opportunity wasn't designed to cover great distances -- its original three-month mission required it to cover about 1 kilometer. That mission was completed in April 2004, but Opportunity has continued to travel and examine ancient Martian environments over that past decade.
"This is so remarkable considering Opportunity was intended to drive about one kilometer and was never designed for distance," said Mars Exploration Rover Project Manager John Callas, of NASA's Jet Propulsion Laboratory in Pasadena, California. "But what is really important is not how many miles the rover has racked up, but how much exploration and discovery we have accomplished over that distance."
The next major landmark on Opportunity's Martian road trip is "Marathon Valley." The investigation site was so-named because if the rover makes it to the location, it will have traveled 26.2 miles -- the distance of a marathon.
In recognition of the Lunokhod 2 mission, the Opportunity rover team selected the name Lunokhod 2 for a crater near the site where Opportunity has been used to conduct research.
"The Lunokhod missions still stand as two signature accomplishments of what I think of as the first golden age of planetary exploration, the 1960s and '70s," said Steve Squyres of Cornell University in Ithaca, New York, and principal investigator for NASA's twin Mars rovers, Opportunity and Spirit. "We're in a second golden age now, and what we've tried to do on Mars with Spirit and Opportunity has been very much inspired by the accomplishments of the Lunokhod team on the moon so many years ago. It has been a real honor to follow in their historical wheel tracks."
Spirit landed at about the same time as Opportunity, but it became stuck in soft soil in May 2009 and has not been heard from since early 2010 -- long after it completed its 90-day mission.
Opportunity, Spirit and the larger rover Curiosity -- which landed on Mars in August 2012 -- are essentially remote-controlled geology research vehicles that receive instructions from mission managers on Earth. Their missions involve exploring Mars' surface and collecting samples for researchers to study as they look for signs of past life.