NASA’s Curiosity Uncovers Striking Polygons at the Bottom of a Martian Hollow

NASA’s Curiosity has been progressively removing layers of Mars’ ancient past from deep within Gale Crater. After over 13 years on the surface, the rover returned to a familiar location known as the Monte Grande boxwork hollow in December 2025. Scientists were eager to have a closer look at the ridges and depressions in this area, so they devised a meticulous plan. As they were wrapping up a weekend excursion, the rover came across something extraordinary.

The cameras acquired some breathtaking shots of a nearby bedrock slab that was covered in polygons. They are constructed up of raised ridges that form these precise geometric shapes. It wasn’t until Curiosity had to get out of the way this time that the team got a clear view; not that they’d been obstructing it for long, but on their previous visit to the adjacent Valle de la Luna site for drilling.

The close-up photographs from the Mars Hand Lens Imager (MAHLI) show an incredible amount of detail; the ridges stand out against the rock, highlighting these interconnecting forms on the top of the block. The lower sections of the block, on the other hand, are a bit more disorganized, which piqued the team’s interest.

We’ve seen polygonal patterns in other areas of Gale Crater. Curiosity went ahead and documented them in the sulfate-rich strata higher on Mount Sharp. Long ago, water and minerals filled in fissures, causing them to develop. These fillings solidified and refused to disintegrate, leaving behind these elevated networks.

However, things are little different in the hollow. The boxwork landscape, with interlocking ridges and hollows, appears to have been formed billions of years ago as groundwater deposited minerals in fissures. Then the wind came along and simply pulled off all the softer stuff, leaving the durable networks exposed.

Curiosity has been gathering data as usual, with its Alpha Particle X-ray Spectrometer and ChemCam laser examining the composition of the polygon centers and ridges, and the team’s 3D model of the block created using a wide MAHLI mosaic. The Mastcam cameras captured stereo views of the hollow walls as well as some fresh light-toned rock. Where the wheels scratched up the ground, that is. Then there’s the sampling; they’ll have to wait and see what it tells us.

It’s not exactly a mystery, since polygons on Mars frequently indicate moist conditions. Some emerge when mud dries out in these repeated wet-dry cycles, resulting in fissures that generate these attractive designs. Others are formed as minerals precipitate in fractures when groundwater runs through them. However, raised instances, such as this one, usually refer to the long-lasting fillings left behind when erosion occurs. Now, this discovery in a boxwork hollow demonstrates the changes that are taking place as Curiosity climbs Mount Sharp. Lakes and rivers continue to have an impact at the bottom. Higher up, it becomes drier, and then there are characteristics like these polygons that reveal where groundwater was still running even after the surface water had disappeared.