NASA’s Curiosity rover has spent roughly six months photographing strange rock formations on Mars that look like massive spiderwebs when viewed from orbit. The low ridges, which stretch for miles across Mount Sharp in Gale Crater, are the clearest evidence yet that mineral-rich groundwater soaked this part of the Red Planet far later than scientists previously believed, billions of years ago. The discovery, announced on February 23, 2026, is now reshaping how researchers think about the timeline of water on Mars and how long potentially habitable conditions may have persisted there.
Boxwork Ridges Stretch for Miles Across Mount Sharp
The formations are a geological feature called boxwork: low ridges standing 3 to 6 feet (1 to 2 meters) tall that crisscross the Martian surface in web-like patterns. From orbit, they resemble giant spiderwebs pressed into the rock. But Curiosity’s ground-level cameras have now confirmed what satellite imagery could only hint at. The ridges extend for miles across the flanks of Mount Sharp, the layered mountain at the center of Gale Crater that Curiosity has been climbing since 2014. According to mission updates from NASA’s Jet Propulsion Laboratory, the rover verified these orbit-seen formations with detailed surface photography over the course of the campaign.
The leading explanation is straightforward but carries large implications. Mineral-rich groundwater once flowed through fractures in the bedrock, depositing a cement-like mineral coating along the crack walls. Over billions of years, the softer surrounding rock eroded away, but the hardened fracture fills resisted, leaving behind the raised ridge network visible today. That process, mineral cementation followed by differential erosion, is well understood on Earth. Finding it at this scale on Mars, and this high up Mount Sharp, tells scientists that groundwater was not confined to the crater floor but reached elevations and time periods they had not accounted for, pointing to a longer and more complex hydrologic history than earlier models suggested.
Close-Up Imaging Reveals Tiny Mineral Nodules
Curiosity did not simply photograph the ridges from a distance. On Sol 4636 (August 21, 2025), the rover’s Mars Hand Lens Imager (MAHLI) captured a mosaic assembled from 50 images using focus stacks to resolve fine surface detail on the ridge faces. The resulting composite shows pea-sized nodules dotting the boxwork textures. Scientists attribute these nodules to minerals that precipitated out of solution as ancient groundwater dried, essentially tiny mineral deposits left behind when the water vanished. The nodules add a second line of physical evidence: the ridges record where water flowed, and the nodules record where it evaporated, locking in a chemical fingerprint of changing conditions.
Earlier in the campaign, on Sol 4536 (May 22, 2025), Curiosity’s Mastcam stitched together a panorama from 23 images that captured the web-like patterns from a wider vantage point across the slope. That panorama established the sheer geographic scale of the boxwork field before the rover moved in for close-up work. Together, the wide-angle panorama and the high-resolution mosaic give the science team both the macro and micro views needed to reconstruct the groundwater system that built these features, tying local mineral textures to basin-scale flow paths through Gale Crater’s sedimentary layers.
Why the Elevation Matters for Mars Water History
Most coverage of this discovery has focused on the visual spectacle of the spiderweb patterns, but the real scientific weight sits in a detail that is easy to overlook: where on Mount Sharp these ridges appear. “Seeing boxwork this far up” the mountain is what excites the mission team, because it suggests groundwater activity persisted later than previously thought. Higher layers on Mount Sharp correspond to younger geological periods. If boxwork only appeared in the oldest, lowest layers, it would confirm existing models that Mars dried out early. Finding it higher up forces a revision: water was active in Gale Crater across a broader span of Martian history, extending the window during which subsurface environments could have been chemically hospitable.
Research from Caltech has used the extent and geometry of boxwork deposits to estimate minimum ancient water volumes associated with Mount Sharp. That work interprets the ridges as early diagenetic features, meaning they formed while the surrounding sediment was still being buried and compacted within a subsurface groundwater zone. The implication is that the water table was not a thin, fleeting presence but a sustained system capable of chemically altering rock across a wide area. Separate doctoral research at Caltech has examined how Curiosity-era observations help reconstruct sedimentary rock formation and diagenesis across Gale Crater, building a broader picture of how water shaped the crater’s geology over time and how multiple generations of fluids may have overprinted one another in the rock record.
A Structured Campaign With Drilling Still Ahead
Curiosity’s investigation of the boxwork field has not been a casual drive-by. The mission team organized the work into a structured multi-phase exploration campaign, with the rover now entering its final phase. That phased approach allowed the team to first survey the formations from a distance, then move in for targeted close-up imaging, and finally select specific drill targets for chemical analysis. One named drill target, “Nevado Sajama 2,” has been identified for sampling, which could yield direct mineral composition data from inside the boxwork ridges rather than relying solely on visual interpretation or remote spectroscopy.
That drilling step is where the current evidence trail hits a gap. Public archives of Curiosity’s imaging data, accessible through the planetary data system, show the extensive photographic coverage of the spiderweb-like ridges but do not yet include a full suite of post-drilling analyses from this specific campaign. Until samples from a ridge interior are powdered and delivered to Curiosity’s onboard laboratories, the team must infer mineral mixes from surface textures and prior experience elsewhere on Mount Sharp. The coming measurements are expected to test whether the ridges are dominated by sulfates, silica, or other cementing agents, a distinction that would reveal whether the ancient fluids were more acidic, neutral, or alkaline and how they interacted with the original lakebed sediments.
Reframing Habitability on the Red Planet
For NASA scientists, the boxwork discovery feeds directly into the broader question of habitability that has driven the Curiosity mission since landing. The rover was sent to Gale Crater to determine whether the region ever offered conditions suitable for life, and the newly documented spiderweb-like ridges add a late chapter to that story. As agency releases have emphasized, Curiosity has already confirmed that ancient lakes once filled the crater, leaving behind clay-rich mudstones and other water-formed rocks. The extensive boxwork now indicates that long after surface lakes disappeared, groundwater continued to circulate through the subsurface, potentially providing a more stable refuge from harsh surface radiation and temperature swings.
Mission scientists note that the combination of boxwork ridges and mineral nodules suggests a dynamic environment in which water not only persisted but changed in chemistry over time. According to a detailed mission summary, the spiderweb-like patterns likely formed as fluids moved repeatedly through fractures, depositing minerals in multiple pulses. Each episode would have altered pore spaces, fluid pathways, and chemical gradients, creating a layered record of water-rock interaction locked inside the ridges. While Curiosity cannot directly detect life, its measurements of these mineral systems help define the duration, stability, and diversity of watery niches that ancient microbes (if they ever existed on Mars) might have been able to exploit.
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*This article was researched with the help of AI, with human editors creating the final content.
