Sometime next week, NASA’s Perseverance rover will officially become the undisputed champion of off-world driving, cruising past 45.16 kilometers (28.06 miles) on the Martian surface. That’s a new record for any vehicle on another world, breaking the previous mark held by the late, lamented Opportunity rover, which stopped talking to NASA back in 2018.
How did Perseverance manage to rack up this kind of mileage in just a third of the time? The answer, as with so many modern miracles, is self-driving technology. "The real enabling technology has been its auto navigation system," Steven Lee, the rover’s project manager at NASA’s Jet Propulsion Laboratory, told Ars Technica.
Just like your cousin’s Tesla, Perseverance uses onboard cameras to image the terrain and algorithms to plot a safe course. Sure, terrestrial self-driving cars have advantages like maps, street signs, and lanes - but they also have other traffic and bad drivers. Mars, by contrast, offers boulders and sandy slopes, but at least no one cuts you off.
The older Curiosity rover, Perseverance’s near-twin launched nine years earlier, had similar imaging and algorithms but was hobbled by a computer a generation older, with some chips dating back to the 1990s. As a result, only about 10 percent of Curiosity’s driving is autonomous - it’s just too slow to think on the fly. In nearly 15 years, Curiosity has driven 38.6 km. Perseverance, with its slightly more modern Vision Compute Element, is about 90 percent autonomous, zipping along at a blistering maximum speed of 150 meters per hour.
Because Perseverance doesn’t have to stop and wait for Earth-bound drivers to send navigation commands, it maximizes its scientific output. "It is very enabling for the science," said Vivian Sun, the mission’s deputy project scientist. "Not to sell the rover’s other advanced capabilities short, but the driving in particular has allowed us to have a larger scope than previous missions."
This self-driving prowess complements its mission perfectly. Curiosity landed in Gale Crater and is leisurely climbing Mount Sharp, stopping frequently to take painstaking measurements. Perseverance, in Jezero Crater, has science objectives that are more spread out, so it cruises from site to site, often arriving ahead of schedule - a pleasant surprise for scientists.
That’s good, because there’s a lot to do. Jezero Crater hosts some of the most ancient rocks in the Solar System, dating back about 4 billion years, older than any on Earth. Back then, Mars was in the late stages of the "heavy bombardment" era, with rocks whizzing around the inner planets, but things were settling down. "It’s the first time we’ve been able to investigate this terrain in situ, and that’s been very exciting," Sun said.
During this era, Mars may have had large lakes and even oceans. Perseverance is exploring to understand what geological and environmental conditions existed and whether the planet could have supported life. Scientists think it might have resembled Earth’s Mojave Desert with water flowing through it, but the debate rages on. Now, there’s lots of data to chew on.
Curiosity is still going strong after nearly 15 years, and Perseverance is doing great too. Curiosity’s wheels showed significant wear and tear after a few years, so Perseverance’s wheels were redesigned - and so far, no appreciable wear, according to Lee. The only minor concern is the wheel actuators, which were life-tested for 20 km of driving but are being certified for at least 100 km, possibly longer. Since Perseverance runs on RTG power and has no consumables or lubricants, Lee says it could keep driving itself across Mars for many years to come - a record that might stand for a while, unless a future rover decides to get ambitious.