Perseverance sets off-world driving record at 28.10 miles

NASA's Perseverance rover has driven 28.10 miles (45.22 km) on Mars, passing Opportunity's 28.06 miles (45.16 km) to become the farthest-driving vehicle on another world. It reached the mark on 11 October, its 2,006th sol, after five and a half years.

Opportunity needed nearly 15 years to get that far. It landed in January 2004 and stopped in 2018, and IEEE Spectrum dates the formal end of its mission to February 2019. Perseverance landed in Jezero Crater in February 2021.

NASA says Perseverance chose its own route for more than 90% of the distance it has covered, against about 5% for Opportunity and Spirit. A command from Earth can take more than 20 minutes to reach Mars, so a rover that picks its own path spends the sol driving instead of waiting for instructions.

Perseverance's wheels are larger in diameter and carry twice as many treads as Curiosity's, a change engineers made after seeing wear on the older rover, NASA's Steven Lee said. It also runs on a radioisotope generator rather than the solar panels that powered Opportunity.

Distance has been accumulating in steps. Perseverance completed the equivalent of a marathon, 26.2 miles (42.195 km), on its 1,890th sol, five years and four months into the mission, NASA said. Opportunity needed 11 years and two months to cover the same distance.

Perseverance has passed every other vehicle driven on another world. The farthest of the Apollo lunar rovers covered 35.74 km (22.21 miles). Curiosity, on Mars since 2012, has logged 23.65 miles (38.06 km). The Soviet Union's Lunokhod 2 drove 24.2 miles (39 km) in 1973.

AutoNav does the steering

AutoNav images the ground while the rover rolls, builds a three-dimensional map of rocks, slopes and sand traps, and picks a safe route between waypoints chosen by planners on Earth. Humans still pick the destinations. Each look processes about 600,000 terrain measurement points; Sojourner, the first Mars rover, managed 20 in 1997. Vandi Verma, a rover planner and driver at NASA's Jet Propulsion Laboratory (JPL), calls the process "thinking while driving". At or near top speed the rover can cover 1,351 feet (412 metres) in a single sol.

Mark Maimone designed the self-driving software for Spirit, Opportunity, Curiosity and Perseverance. He told IEEE Spectrum that Spirit drove itself 23% of the time and travelled 50% faster when it did, while Opportunity and Curiosity used autonomous driving about 5% of the time. Perseverance is the first Mars rover to drive itself 90% of the time.

What the record does not mean

Perseverance is not fast. Engadget puts its maximum speed at about 0.1 mph; Maimone told IEEE Spectrum it drives itself at up to 120 metres an hour.

The mission was never planned around distance. Steven Lee, project manager for the Curiosity and Perseverance rovers at JPL, said the original mission called for no more than 12.4 miles (20 km) of driving, and Perseverance has gone more than twice that far. Lee said all mobility systems remain fully operational and that extended ground-life testing supports years more driving. NASA approved the mission's first extension, which began in October and runs through roughly the end of 2028.

Where the rover is heading

The record fell while Perseverance was crossing Lac de Charmes, on the western rim of Jezero Crater, on its way to a site called Idubi. The team hopes to find traces of ancient hydrothermal systems there.

Ken Farley, a professor of geochemistry at Caltech and a former project scientist on the mission, told ScienceAlert the rocks are "probably older than 4 billion years". NASA says the rover has collected 29 rock and soil samples on the way. A possible biosignature in a rock nicknamed Cheyava Falls remains a candidate rather than proof that life existed.

After Lac de Charmes, the plan points south toward Rainbow Falls, a 100-metre-wide block of ancient crust lifted by the impact that formed Jezero Crater.