Perseverance rover selfie from early 2023.
Sometimes Mars feels like the setting for a Dr. Seuss book, full of fantastical shapes and strange landscape features that seem to defy gravity. NASA is an eyewitness to just how weird Mars can be as evidenced by a “mushroom” rock spotted by the Perseverance rover.
A red circle shows the mushroom-shaped rock seen by NASA's Perseverance rover in June 2022.
There’s a lot we can learn from a tiny mushroom-shaped rock. Caltech doctoral student Hemani Kalucha highlighted the unusual rock in a Perseverance mission update on March 11. Look closely and you’ll see a thin stalk with a rounded “cap” on the top. The rock is throwing a shadow underneath it that shows how it's standing up from the flatter rock below.
The "mushroom" rock is tiny, but here's a closer look.
The rock is performing a delicate balancing act. “The ‘mushroom’ is actually a geologic feature known as a concretion,” Kalucha explained. “Concretions are solid masses within a rock that form as water flows through sediment, dissolving minerals and reprecipitating them in a more compacted configuration.” There’s more to the rock’s story. The hard, erosion-resistant concretion persisted while wind carved away the softer material around it.
The image is one of a group taken on the same Martian day showing a sandy field of rocks of different shapes and sizes. The fungus-like rock is not even half an inch wide. So how did the tiny “mushroom” get noticed? The Perseverance team “was on the hunt for concretions in this rock unit and everyone was zooming into all the images coming down from the rover each day very closely,” says Kalucha over email.
The mushroom-rock image comes from 2022 when the rover was exploring a region called Hogwallow Flats inside of the Jezero Crater. Hogwallow is packed with fascinating formations. “The rocks at Hogwallow Flats appear to be very fine-grained, which is exciting to scientists on the mission as fine-grained rocks may have the best chance at preserving evidence of life,” said Perseverance team member Lydia Kivrak in a mission update in 2022.
The rock may look a lot like a mushroom, but it’s not an actual fungus. Though Mars has an intriguing history of water, the modern-day planet is an inhospitable place. It’s cold, windy, dusty and dry on the surface. Robotic explorers have yet to find definitive evidence of life, current or ancient.
One of the goals of the Perseverance mission is to understand if life ever existed on Mars. The rover isn’t equipped to answer that question on its own, so it’s been collecting rock samples for future return to Earth. NASA’s proposed Mars Sample Return mission, however, is in financial limbo. If NASA pulls it off, it will put Martian rocks into labs so scientists can look for evidence of ancient microbial life.
Mars has a way of surprising space fans. NASA’s Curiosity rover—which is exploring a different crater on the red planet—encountered a suspended “spoon” in 2015, Kalucha noted.
Suspended "spoon" rock casts a shadow in this Curiosity rover image from 2015.
Kalucha described the mushroom-like formation as “my favorite rock on the mission so far.” That’s high praise considering the incredible sights Perseverance has sent back since arriving on Mars in early 2021. The rover photographed some goofy-looking rocks that resemble sea creatures and a formation that looks like an avocado or sombrero. There are plenty of opportunities to let your imagination run wild when it comes to Mars, but sometimes a mushroom-shaped rock is just a mushroom-shaped rock.
