For NASA's Perseverance, roaming Mars is a lonely existence, but the rover now has a traveling companion: a hitchhiking "pet rock" that got lodged in one of its wheels.
Fortunately, the Martian stone will not interfere with the rover's research mission and will simply be a little annoyance — similar to a rock trapped in your shoe.
According to NASA, the pet rock was picked up by Perseverance's front-left wheel on Feb. 4, or Sol 341 — the 341st Martian day of the Martian year.
The rock has occasionally photobombed the rover's front-left Hazard Avoidance Camera photographs (Hazcam).
The boulder is still sliding along with Perseverance 126 days (123 sols) after it originally caught a ride, according to recent photos. (A Martian day, or sol, is only 37 minutes longer than an Earth day.)
For well over a quarter of Perseverance's journey on Mars, the rock has been traveling with the rover. The rover was studying the Máaz formation - a portion of the Jezero crater that experts believe is made up of ancient lava flows – when the rock initially made its home in Perseverance's wheel.
Since then, Perseverance has gone 5.3 miles (8.5 kilometers) via the Octavia E. Butler landing site, where it initially landed on Mars in February 2021, and through the ruins of the Kodiak delta, which once connected an ancient river and lake.
The rover will soon be preparing for a climb up one of the Jezero crater's high slopes, which might cause its rocky stowaway to fall out.
Because the pet rock is likely of volcanic origin, it will be surrounded by rocks that are substantially different from itself when it ultimately falls out of the rover's wheel.
"We might confuse a future Mars geologist who finds it out of place," according to the statement, one mission scientist quipped in a recent conference.
During its mission, Perseverance, or Percy, has taken up a few more tiny rocks in its front-right wheel, but they have all dropped out within a few days or weeks.
According to the announcement, this makes the newest pebbly traveler a Martian hitchhiking record-breaker.
However, Percy isn't the only Mars rover that has found a pet rock.
NASA's Spirit rover, which wandered Mars from January 2004 to March 2010, had to undertake a rapid turn maneuver in December 2004 to shake loose a "potato-sized" boulder from its right-rear tire, which scientists worried might cause serious damage, according to NASA.
Perseverance's previous problems with scooping up undesirable rocks in other portions of the rover were even more problematic.
