Few things are as annoying as a pebble in your shoe that you just can't shift. Turns out, this extremely Earthly issue is also a problem on Mars, as the rover Perseverance has discovered.
The interloper – a small rock – was snapped lodged inside one of the rover's six aluminum wheels by its Onboard Front Left Hazard Avoidance Camera on February 25, 2022. Thanks to some digging through NASA's raw images by C|Net reporter Amanda Kooser, it appears to have been there since at least February 6. Most likely the rover kicked it up while trundling around Jezero Crater, where it’s been exploring since February last year.
Can't Percy just kick it out? It was photographed again on March 2, so apparently not – though it doesn't seem to be hindering the rover, instead just adding to its traveling companions.
It's possible the rock was picked up during Perseverance's first long AutoNav drive. In February, the rover broke the record for most distance traveled in a single day by a Mars rover at 320 meters (1,050 feet) using its auto-navigation function.
It's unlikely the rock is affecting the rover's performance – Perseverance is, after all, the "biggest, heaviest, cleanest, and most sophisticated six-wheeled robotic geologist ever launched into space."
Its wheels – designed to withstand the wear and tear seen on Curiosity's – are 52 centimeters (20.4 inches) wide, with titanium spokes, built to withstand regolith from another planet. T’is but a rock.
“It’s not perceived as a risk. We’ve seen these kinds of rocks get ‘caught’ in Curiosity’s wheels from time to time, too,” a JPL spokesperson told Gizmodo. “They occur during cross-slope drives, and tend to fall out entirely on their own after a while (there’s no particular way to get this rock out of our ‘shoe’). These kinds of rocks don’t impact driving other than making it a bit noisier.”
So, will Percy bring its little travel companion back home with it? Gulp, Percy isn’t coming home. However, it is collecting rock samples to send back to Earth, with an estimated launch home date of 2026 and an arrival back on Earth of 2031.
Here's hoping NASA scientists crack into those Mars rock samples sooner than they have done with their lunar samples, we'd like to still be alive to see what they discover.