NASA’s Perseverance Rover Unveils Mysterious Martian Rock: What Hollow Spherules Reveal About Mars

This month, NASA’s Perseverance rover made an exciting find on Mars. While exploring the Jezero Crater, the rover discovered an unusual rock covered with dark gray spheres, some of which have tiny holes. This has caught the attention of scientists eager to understand more about Mars’s history, especially its past water activities and geological events.

The intriguing rock, named St. Pauls Bay, was found on March 11, 2025, during Perseverance’s journey around Witch Hazel Hill, near Broom Point. While the region had already been researched from orbit, the rover’s close-up examination revealed this peculiar sample. The texture is remarkable—it features hundreds of small, spherical shapes, some perfect, and others elongated or jagged, with a few sporting tiny pinholes.

Alex Jones, a PhD candidate at Imperial College London, raised an important question: “What geological processes could lead to these unusual shapes?” This discovery is prompting scientists to re-examine theories about St. Pauls Bay and its possible origins.

This isn’t the first time Mars has revealed rocks with spherules. The Opportunity rover found similar formations, nicknamed “Martian blueberries,” in 2004. Curiosity, another Mars rover, also discovered spherules in the sedimentary rocks of Gale Crater. Perseverance had previously reported popcorn-like spherules in the inlet channel of Jezero Crater. Generally, these formations have been interpreted as concretions—mineral nodules formed from groundwater interaction over long periods.

The team studying St. Pauls Bay is looking at two main theories for how the spherules formed:

• Groundwater Interaction: These might be concretions created from the slow action of fluids depositing minerals inside rocks. If true, this could show signs of the planet’s ancient water activity, which is crucial in understanding Mars’s environment.
• Volcanic or Impact Origin: Alternatively, they might be the result of volcanic eruptions or meteorite impacts, where molten rock cools rapidly to form these shapes. This type of formation usually results in jagged edges, similar to the features observed in this rock.

Both theories imply different histories for Mars. NASA emphasizes that understanding these origin processes is essential for grasping how Mars’s landscape has evolved over time.

An important detail is that St. Pauls Bay is a “float rock,” meaning it’s not situated in its original place but moved from where it formed. The Perseverance team suspects it comes from older, dark-toned layers seen in the vicinity. If true, this would connect the rock to ancient geology not yet explored.

French geologist Gwenaël Caravaca, who has worked on the Curiosity and Mars 2020 missions, pointed out the importance of this location: “These terrains outside the crater are among the oldest ever explored on Mars—dating back to the Noachian, over 3.7 billion years ago.” Studying rocks from this time might shed light on the planet’s oldest features, untouched by the more recent geological activity seen within the crater.

As NASA scientists search for links between the rock and specific geological layers in Witch Hazel Hill, they hope to deepen their understanding of Mars’s past. Determining whether St. Pauls Bay is part of a broader geological layer could reveal a lot about the planet’s history of water, volcanic activity, or other phenomena.

The excitement around Perseverance’s discovery highlights the ongoing intrigue of Mars. This spherule-covered rock could be a remnant of ancient water flows, a piece of volcanic history, or evidence of a meteorite strike. Whatever its origin, St. Pauls Bay serves as a reminder of how much we still have to learn about our planetary neighbor.

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