NASA Mars Scientists Ponder 'Peculiar Pale Pebbles' Mystery

Pebbles are scattered all over Earth. Mars has plenty of pebbles too. They may seem like a mundane bit of geology, but a specific clutch of pebbles spotted by NASA's Perseverance rover captured scientists' attention. In late October, the rover photographed a scattering of bright white rocks. The Martian pebbles present two big mysteries: What are they made of, and how did they get there? 

Bright white pebbles are no big deal on Earth. "On Mars however, with its lack of plate tectonics and a basaltic crust dominated by dark minerals like olivine and pyroxene, white rocks are a rare find," NASA said in a Nov. 12 statement. The rover team referred to the rocks as "peculiar pale pebbles."

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Perseverance rover poses for a selfie with a sample tube as it builds the first sample depot on another planet.

Perseverance has been in residence on Mars since early 2021. The rover is exploring a new area of the Jezero Crater. It spent time down below checking out an ancient river delta and in August embarked on a dramatic climb to the crater rim. 

That's when the Perseverance team noticed "increasingly diverse and strange-looking rocks" as the wheeled explorer ascended. The white pebbles are situated along a mound in the crater rim. The team nicknamed the spot Mist Park.

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The science team directed Perseverance to investigate the rocks through imaging and with its Supercam, a laser-equipped instrument used to study the chemical and mineral compositions of rocks. Researchers would love to get a closer look at the odd rocks. 

"Unfortunately, none of the rocks were big enough to safely inspect them up close with Perseverance's robotic arm instruments, but the team is on the lookout for larger blocks or outcrops of this strange lithology as we continue traversing upslope," NASA said.

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The white rocks don't match the surrounding scenery, so scientists are questioning how they got there. They may have been left behind by erosion processes or perhaps fallen down a slope. 

Perseverance is not just hanging out on the red planet for sightseeing -- though it's very good at it. The rover is trying to help us answer the question of whether Mars may have hosted microbial life long ago. It's been collecting rock samples NASA hopes to bring back to Earth for closer study. 

Perseverance is living a rocky life on Mars. It's had pet rocks riding along in its wheels. It spotted intriguing evidence of organic matter in rocks. It's constantly climbing over rocks as it travels. Mission scientists see a lot of rocks, so rocks have to be pretty special to get a call-out. The white pebbles will remain a mystery for now, but this likely isn't the last we'll hear of them.