NASA’s Curiosity rover has taken stunning new images of giant “spider webs” that zig-zag across the surface of Mars. One of those images has revealed never-before-seen egg-like spheroids covering the scattered structures — and scientists are struggling to explain them.
Over the past 8 months, Curiosity has been carefully examines a series of interconnected stone ridgescalled “boxwork”, on the slopes of Mount Sharp, in Gale Crater. These ridges, which cover an area up to 20 kilometers in diameter, were created billions of years ago when ancient Martian groundwater seeped beneath the planet’s surface. They were first discovered by spacecraft in orbit in 2006, but they have remained largely unexplored until now.
The web-like structures are not to be confused with the infamous “spiders of Mars” – a series of geological features created when carbon dioxide freezes sublimates beneath the Red Planet’s surface and looks like swarming arachnids seen from above. (These fake spiders were too newly recreated on earthwhile a similar “wall demon” was as well discovered on Jupiter’s moon Europa.)
NASA released Curiosity’s first box pictures in June 2025, shortly after reaching the rocky ridges. But on Monday (February 23), the agency released two more snaps, showing the structures in much greater detail.
One of these images, taken last September 26, shows a ground level view of the ridges, which stand 3 to 6 feet (1 to 2 meters) above the surface of Mars. But another close-up image, taken on August 21, revealed that some of these ridges are covered in small irregularly shaped lumps, or nodules, that have not been seen until now.
These nodules bear a striking resemblance to minispheroids the surface of a mysterious “spider egg” stonewhich was discovered in the Jezero crater by NASA’s Perseverance rover last year and has an unknown origin. And scientists are also having a hard time explaining exactly how the tiny box “eggs” were formed.
“We can’t quite explain yet why the knots appear where they do,” Tina Seegera planetary scientist at Rice University in Houston who directs Curiosity’s boxwork surveys, said in a statement. “Perhaps the ridges were cemented by minerals first, and later episodes of groundwater left nodules around them,” Seeger said. But more work is needed to confirm whether this is the case.
But while the knots and box have an eerily biological appearance, there is no suggestion that they have any direct ties to extraterrestrial life.
Mars spider web
Boxwork consists of intersecting ridges of mineral-rich rocks that litter the surface of Mars. Similar but smaller structures are found on Earth, mainly in caves, and are formed when calcite-rich water flows between rocks that eventually erode, much like how stalagmites and stalactites form, according to National Speleological Society.
On Mars, however, the box was shaped by the violent winds that scour the planet’s surface: “The bedrock beneath these ridges was likely formed when groundwater seeping through the rock left behind minerals that collected in these cracks and crevices, solidifying and becoming cement-like,” NASA officials previously written. “Eons of sandblasting by Martian winds wore away the rock but not the minerals, revealing networks of resistant ridges within.”
The team is particularly interested in the patch of boxwork on Mount Sharp because it formed in isolation and is surprisingly high up on the mountain’s slopes, which has implications for the planet’s confusing watery past.
“Seeing boxwork this far up the mountain suggests that the water table had to be pretty high,” Seeger said. This suggests that the water in this area may have “lasted a lot longer than we thought,” she added.
Scientists hope that further investigation will also shed light on the specific conditions that formed these structures and whether they may have been favorable for any potential ancient Martian microbes.
“These ridges would include minerals that crystallized underground, where it would have been warmer, with salty liquid water flowing through,” Kirsten Siebacha Curiosity mission researcher at Rice University who has also studied the area, previously said. “Early soil microbes could have survived in a similar environment. That makes this an exciting place to explore.”
Uneven terrain
While the final phase of Curiosity’s mission is yielding fascinating results, it is also proving to be one of the most difficult to navigate.
The box job is arguably the toughest terrain the car-sized robot has had to traverse since it landed in Gale Crater in 2012. The rover must balance along the ridges “like a highway” and avoid sliding “down into the caves” between them, Ashley Stroupea systems engineer at NASA’s Jet Propulsion Laboratory in Southern California, said in the statement.
The task of controlling the rover has also become increasingly challenging because of a gaping hole in one of the robot’s wheels, which was first discovered in late 2024.
“There’s always a solution,” Stroupe said. “It just requires trying different avenues.”
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