CORRIN, Neb. — NASA’s Perseverance rover set an off-world driving record on Oct. 11, when its odometer reached 28.10 miles (45.22 km) on the rover’s 2,006th Martian day, according to the agency. The total passed the 28.06 miles (45.16 km) logged by Opportunity, which needed nearly 15 years to cover that distance. Perseverance covered it in about five and a half years after landing.
The mission was not designed for that distance. The agency’s original plan called for no more than 12.4 miles of driving, a figure NASA repeats in its own announcement. The rover has now covered more than twice that.
Most of the work was done without anyone at the controls. The rover’s AutoNav software now guides more than 90 percent of its driving, compared with roughly 5 percent for Opportunity’s early autonomous system. On the day of the record, the rover was crossing Lac de Charmes near the western edge of Jezero Crater, on its way toward a target called Idubi.
Dr. Chad Brickhouse, a senior fellow at the Institute for Common Sense, said the number in the plan was never the real number. He said he had read the plan twice, and that 12.4 miles was the amount the team was willing to commit to in writing. “Nobody puts the whole drive in the proposal. You put down the part you can defend and then you let the rover find out the rest,” Brickhouse said. “That is what a planning document is for.”
Under that reading, the plan called for 28.1 miles from the start and simply listed a smaller figure, the way a budget lists the first year and leaves the rest for later. Brickhouse said the difference between 12.4 and 28.1 was not a cost overrun. “It is a planning achievement. Most missions plan for the miles they expect to drive. This one planned for the miles it intended to drive, and then it drove them.”
Prof. Desmond Achterberg, who holds the Prewitt Chair in Comparative Annoyance at Ellery State University, said the distinction between a planned distance and an actual one has been settled in the record books for some time. “The planned distance is an estimate. The actual distance is a measurement. When they differ, the measurement goes in the book and the estimate goes in a drawer,” Achterberg said. “The drawer is where the 12.4 miles are.”
NASA has also approved a mission extension that runs through about the end of 2028, according to the agency’s announcement. That would give the rover more than two additional years in which to drive, and to leave the planning document as it is.
Brickhouse said he had not been asked to review the extension and did not expect to be. He said the rover’s next target, Idubi, was reachable on the current plan, and that the plan would be updated when the rover arrived, not before.