NASA's Perseverance rover lost its pet Martian rock
NASA's Perseverance rover has dropped the 'pet rock' that had been tagging along with it for some time now.
For over 14 months now, as the Perseverance rover has been exploring Jezero crater on Mars, a sizeable rock has been bouncing and sliding around in its front left wheel. First showing up in hazard avoidance camera images on February 6, 2022 (Sol 343 or the 343rd Martian day of the rover's mission), the NASA team dubbed this stone the rover's 'pet rock' after it continued to appear in hazcam images for over 4 months.
This image from NASA's Mars Perseverance rover shows the view captured by its front left hazard avoidance camera, on February 6, 2022, showing a large stone resting in the bottom of its front left wheel. Credit: NASA/JPL-Caltech
Since then, this pet rock has gone everywhere with Perseverance: as the rover gathered multiple science samples, as it dropped those samples off at 'Three Forks', where some future mission will pick them up for return to Earth, and then as it climbed up the western fan of Jezero's river delta.
However, in images downloaded on April 18, 2023 (Sol 768), the pet rock was gone!
This map of Jezero crater on Mars shows the path of the Perseverance rover since it landed on February 18, 2021. First heading south, the rover explored the perimeter of a rippled sandy area, picked up its pet rock on February 6, 2022, then headed north, and curved to the west to investigate the base of the river delta fan before climbing up and arriving at the crater named Belva on top of the delta in mid April 2023, where it dropped the pet rock! Credit: NASA/JPL-Caltech/Scott Sutherland
"Farewell 'Rock Friend'," Dr. Gwénaël Caravaca, a planetary geologist who is on the Perseverance mission team, said on Twitter. "We found out in latest Hazcam we have lost our pet rock in the front left wheel of @NASAPersevere. It spent 427 Sols with us (more than an Earth year!), and traveled about 10 km since Sol 341. Farewell Rock Friend, you will be missed!"
There's no way to know for sure exactly what caused the rock to be ejected from within Perseverance's wheel. It's possible that sand may have elevated the rock just enough that it could slip over the wheel rim.
This image from Perseverance's left hazcam shows a mound of sand inside the rover's wheel, and hard stones that the rover is driving over. Credit: NASA/JPL-Caltech
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Even when the Perseverance team first recognized the pet rock, one member was quoted as saying "we might confuse a future Mars geologist who finds it out of place!" At that time, the rover was still exploring the base of the delta.
Now, the rock has travelled over 10 kilometres from its original location on the crater floor to a point atop the delta the mission team calls Echo Creek. That hypothetical future Mars geologist is definitely going to need some context if they ever spot this 'strange' rock lying there.
This composite image shows the Perseverance rover's view of the impact crater named Belva, which is located on top of the dried-up river delta at the west end of Jezero Crater on Mars. The shadow of the rover's mast is visible along the bottom of the image. Credit: NASA/JPL-Caltech/Scott Sutherland
This isn't the only rock Perseverance has picked up as it has roved around Jezero crater.
On February 27, 2023, as the rover was driving up the slopes of the river delta, another sizeable stone appeared in its front right wheel. Although it appeared even larger than the first one, this one didn't stay around long enough for NASA to flag it as another pet rock. It disappeared just two days before the pet rock was ejected from the left wheel.
These two views show Perseverance's front right wheel on April 8 (left) and April 16, 2023 (right), revealing what is probably the best view of this second rock before it disappeared. Credit: NASA/JPL-Caltech
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Plus, since March 12, 2023, another Martian rock has been hitching a ride with Perseverance, in the rover's rear left wheel. It remains to be seen how far this rock will travel, though.