‘Spiderwebs’ Might Rewrite What We Know About Water on Mars

For more than a decade, NASA’s Curiosity rover has been climbing a Martian mountain, reading the planet’s ancient history layer by layer.

Now, a discovery of web-like rock formations and tiny egg-shaped mineral deposits clinging to them is changing what scientists thought they knew about how long water persisted on the Red Planet.

Six Months In an Alien Landscape

NASA’s Curiosity rover has spent roughly six months exploring a geological feature on Mars known as boxwork: a vast network of low rock ridges, about 3–6 feet (1–2 meters) tall, crisscrossing the surface for miles with sandy hollows nestled between them.

From orbit, the formations look like giant spiderwebs etched across the terrain. From the ground, they take on a more tangible quality.

“These ridges are maybe two parking spaces wide, and they stand 3 to 6 feet tall above the sandy hollows between them. So would be a pretty fun landscape to ride your BMX bike across,” Tina Seeger told News 2’s sister station, NewsNation.

The science behind them, though, goes far beyond their appearance.

These ridges suggest that groundwater existed on Mars later than scientists previously believed, raising questions about how long water persisted on the planet and how long microbial life might have survived billions of years ago — before Mars became the dry desert we see today.

How the ‘Spiderwebs’ Formed

Before Curiosity reached the boxwork region, scientists only had orbital images of the formations. Their exact structure and composition were uncertain.

With the rover now on the ground, detailed images and samples have revealed a clearer picture.

Scientists believe the boxwork formed through a multi-step process spanning vast stretches of time. Groundwater flowed through fractures in bedrock, depositing minerals in those fractures.

The mineral deposits strengthened certain areas of rock. Over time, wind erosion stripped away the weaker surrounding rock, leaving the hardened areas standing as raised ridges.

What remains is a landscape of resilient mineral-cemented walls — a record of a wetter Mars where liquid water once moved through underground channels and left its chemical signature behind in stone.

Reading Climate History on Mount Sharp

The formations sit on Mount Sharp, a towering feature about 3 miles (5 kilometers) tall that Curiosity has been steadily ascending.

Each layer of the mountain represents a different period in Mars’ climate history, making it something like a geological textbook the rover reads as it climbs.

As Curiosity has moved higher, the environment it encounters shows signs that water gradually disappeared over time, with occasional periods of returning rivers and lakes. Finding boxwork this high up the mountain carries particular weight.

“Seeing boxwork this far up the mountain suggests the groundwater table had to be pretty high,” said Seeger of Rice University in Houston, one of the mission scientists leading the boxwork investigation. “And that means the water needed for sustaining life could have lasted much longer than we thought looking from orbit.”

If groundwater extended higher up the mountain and lingered longer than previously understood, it expands the window during which conditions on Mars could have supported life.

Egg-Like Nodules in Unexpected Places

Curiosity’s ground-level investigation also uncovered something scientists didn’t anticipate.

Among the ridges and hollows, the rover found small mineral nodules — bumpy, pea-sized formations that are typically signs of ancient groundwater activity.

Finding such nodules wasn’t itself a surprise. What caught scientists’ attention was where they appeared.

Instead of clustering near the fractures where groundwater once flowed, the nodules turned up along ridge walls and inside the hollows between ridges.

Scientists do not yet fully understand why. One possible explanation: the ridges may have been cemented by minerals first, and later groundwater activity could have created nodules around them in a separate phase. The puzzle remains open.

Navigating Treacherous Terrain

Driving through the boxwork is no simple feat. The ridges are barely wider than the rover itself, and Curiosity weighs 899 kilograms.

Rover drivers at NASA’s Jet Propulsion Laboratory in Southern California, which built Curiosity and leads the mission, must carefully guide it across ridge tops and then down into sandy hollows.

Wheels can slip in the sand. Turning in narrow spaces is difficult.

“It almost feels like a highway we can drive on. But then we have to go down into the hollows, where you need to be mindful of Curiosity’s wheels slipping or having trouble turning in the sand,” said operations systems engineer Ashley Stroupe of NASA’s Jet Propulsion Laboratory. “There’s always a solution. It just takes trying different paths.”

Every day, a team of engineers and scientists on Earth plans each careful move of a robot millions of miles away, solving problems they couldn’t have predicted when the mission was designed.

New Images Sharpen the Picture

NASA released Curiosity’s first boxwork photos in June 2025, shortly after the rover reached the rocky ridges. On Monday (Feb. 23), the agency released two more images showing the structures in much greater detail.

These close-up shots revealed the pea-sized nodules and the intricate textures of the ridges themselves, giving scientists their clearest view yet of how ancient groundwater reshaped this part of Mars.

The rover is expected to leave the boxwork behind in March, continuing its climb up Mount Sharp.

For those who have followed Mars exploration across decades — from the first grainy images sent back by early spacecraft to Curiosity’s high-definition panoramas — the boxwork discovery feeds directly into a question that has captivated generations: Was there ever life on Mars?

Seeger put it plainly.

“We all need water. All sorts of microbes need water. So our investigation on Mars has been about looking for signs that there was water and signs that it was a neutral pH, a good temperature, where microbes could have lived,” Seeger said.

“So, now that we see this evidence for later-stage groundwater where we could have maybe had microbes living in the subsurface, if they were there, we can keep looking for fossil evidence,” she added.

If water lingered longer than scientists thought, the conditions for microbial life may have persisted longer too.

The chance of finding fossil evidence of that life, somewhere in the ancient layers of Mount Sharp, remains very much alive.

Curiosity rolls on.

Production of this article included the use of AI. It was reviewed and edited by a team of content specialists.