A Mars rover has sadly lost its pet rock.
The Martian stone has been hitching a ride on Perseverance for more than half its time on the Red Planet.
It was spotted by NASA boffins last year, who called it an "unexpected traveling companion".
However, Mars fans have noticed the absence of the rock in recently beamed back images.
A bittersweet image taken on 18 April shows the small passenger missing from the wheel.
Dr. Gwénaël Caravaca, a Martian geologist, commented online: "Farewell 'Rock Friend'.
"We found out in latest Hazcam we have lost our pet rock in the front left wheel of NASA Perseverance.
"It spent 427 Sols with us (more than an Earth year!), and travelled about 10 km since Sol 341.
"Farewell Rock Friend, you will be missed!"
Last June, NASA noted: "In early February— a rock found its way into the rover’s front left wheel, and since hitching a ride, it’s been transported more than 5.3 miles (8.5 km).
"This rock isn’t doing any damage to the wheel, but throughout its (no doubt bumpy!) journey, it has clung on and made periodic appearances in our left Hazcam images."
At the time, the space agency pondered where the rock might end its journey, explaining: "It’s possible that the rock may fall out at some point along our future ascent of the crater rim. If it does so, it will land amongst rocks that we expect to be very different from itself.
"As one of our team members quipped this week, “we might confuse a future Mars geologist who finds it out of place!”
They added: "So: if you’re a Martian geologist from the future reading this, maybe a Martian graduate student tasked with mapping the historical site of Jezero crater: take heed. If you’ve found a rock that looks out of place, you might just be looking at the former pet rock of Perseverance!"
