By Edwin Anang
They resemble a dish of lentils—or perhaps a cluster of spider eggs on a leaf.
But whatever these tiny brown spheres are, their sudden appearance on the surface of Mars has left NASA scientists scratching their heads.
New images captured by the Perseverance rover in March reveal an alien-looking rock formation made up of hundreds of small, spherical objects. Each sphere is just millimeters in diameter, yet their presence has raised big questions among planetary scientists.
Despite extensive experience studying Martian geology, researchers say they’ve never seen anything quite like this. The spheres appear scattered across a rock outcrop along the rim of Jezero Crater, standing out starkly against the surrounding rusty red dust of the Martian landscape.
These peculiar formations may hold clues to the Red Planet’s deep volcanic and geologic history, stretching back 4.6 billion years. Mars, once home to thousands of massive volcanoes, experienced violent “super eruptions” that could have shaped its surface in dramatic ways.
The latest discovery follows earlier images of “araneiforms”—dark, spider-like cracks in the Martian soil that have no direct comparison on Earth.
The new images were taken on March 11 and 13, 2025—Sols 1442 and 1444 of the mission—by Perseverance’s onboard camera. One shows a rock littered with smooth, rounded nodules. Another reveals a similarly out-of-place boulder resting in a Martian crater, as if it had arrived from somewhere else entirely.
“The Perseverance Science Team was astonished by a strange rock comprised of hundreds of millimeter-sized spheres,” said Alex Jones, a PhD student from Imperial College London’s Department of Earth Science, in a NASA blog post.
“Placing these features in geologic context will be critical for understanding their origin and determining their significance for the geological history of the Jezero Crater rim and beyond.”
Technically, the formations are called spherules—tiny, roughly spherical pebbles that range from 0.01 mm to 4 mm (about 0.15 inches) in diameter. Some are perfectly round, others elliptical or angular, with a few even containing pinhole-sized perforations. The diversity in their shapes and textures adds to the mystery.
On Earth, similar spherules can form in two primary ways:
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Volcanic eruptions, where molten rock rapidly cools into droplets
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Meteorite impacts, where the intense heat vaporizes rock, which then condenses into small spheres
Understanding how these Martian spherules formed could offer critical insight into the environmental conditions of ancient Mars.
Dr. Matthew Chojnacki, a planetary geologist at the Planetary Science Institute, suggested they may be frothy lava that cooled quickly. But, as he pointed out, it’s hard to be sure without further chemical or mineralogical analysis—especially since this is a “float rock”, meaning it’s not anchored to the local bedrock and may have traveled from elsewhere.
This isn’t the first time mysterious spheres have turned up on Mars.
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In 2004, NASA’s Opportunity rover discovered the now-famous “Martian blueberries”—iron-rich spherules at Meridiani Planum.
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In 2012, the Curiosity rover found similar features embedded in rocks at Gale Crater.
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In 2024, Perseverance observed “popcorn-like” textures in sedimentary rocks in the Jezero Crater’s Neretva Vallis channel.
Each of these discoveries deepens our understanding of Mars’ rich and complex history—and raises new questions about how similar, or alien, the planet truly is.
Perseverance, which landed in February 2021 after a nearly seven-month journey, continues its mission to search for signs of ancient microbial life and collect samples for eventual return to Earth. The rover’s current home, Jezero Crater, is thought to have once hosted a lake and river delta system—a promising site in the quest for Mars’ ancient secrets.
As researchers continue analyzing these odd spherules, one thing’s for sure: Mars is still full of surprises.
