NASA’s Perseverance rover takes amazing photos, but also  studies and collects Martian rocks. Apparently, one rock in particular really wanted to be part of the mission. It hitched a ride in Perseverance’s wheel and has been there for four months. In that time, the rover has traveled 5.3 miles. Perseverance has photographed ancient lakebeds and the lumpy Martian moons. But all eyes are now on the front left wheel to check if Percy’s pet rock is still along for the ride. 

A photo of the wheel of the Perseverance rover with a rock sitting in it
NASA/JPL-Caltech

Graduate student Eleni Ravanis wrote the NASA blog post sharing the news and photos. She is clearly a great science communicator with a sense of humor. The post includes details about the rock’s journey over the past 120 sols (Martian days). But it also has a warning to future researchers. After all, the geology on Mars is diverse. Wherever the rock finally does fall out, it will likely be among very different terrain from where it was picked up. The rover will eventually climbing the slopes of the crater, which could set the pet rock free.

“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,” writes Ravanis. “If you’ve found a rock that looks out of place, you might just be looking at the former pet rock of Perseverance!”

NASA/JPL-Caltech

Previous Mars rovers Spirit and Curiosity also picked up hitchhiking rocks during their journeys. However, they didn’t stick around long to become pets. Hopefully someone on the NASA Perseverance team has read the 32-page training manual for Pet Rocks (which you can apparently still buy). Even experience with a Chia Pet could help.

Melissa is Nerdist’s science & technology staff writer. She had a pet rock with googly eyes back in the ’80s. Melissa also moderates “science of” panels at conventions and co-hosts Star Warsologies, a podcast about science and Star Wars. Follow her on Twitter @melissatruth.