NASA’s Curiosity Mars rover discovered these rugged, pea-sized lumps while exploring an area filled with boxwork formations — low peaks about 3 to 6 feet (1 to 2 meters) high with sandy depressions in between. The mosaic is composed of 50 individual images taken on August 21, 2025, the mission’s 4,636th Martian day, or sol, by Curiosity’s Mars Hand Lens Imager (MAHLI), a camera on the end of the rover’s robotic arm. Ten images were taken at different focus settings at each of five locations to produce a sharp mosaic. The images were stitched together after being sent back to Earth.
Figure A is the same image with a smaller scale bar added to the right.
Such objects have been seen many times before on the Red Planet, including by Curiosity. They were formed billions of years ago from the minerals left after water dried up. Crossing the surface for miles, boxwork formations reveal that ancient groundwater flowed on this part of the Red Planet later than expected, raising new questions about how long microbial life could have survived on Mars, billions of years ago, before rivers and lakes dried up.
Boxwork ridgetops often include a deep line the team refers to as a “central fracture,” where groundwater originally seeped through a rock crack, allowing minerals to concentrate. Surprisingly, the mission did not find any nodes near these central fractures. Instead, they were found along the walls of ranges and in the hollows between them. The wavy ridges between groups of nodules are mineral veins composed of calcium sulphate, which is also deposited by groundwater.
Curiosity was built by NASA’s Jet Propulsion Laboratory, which is managed by Caltech in Pasadena, California. JPL leads the mission on behalf of NASA’s Science Mission Directorate in Washington as part of NASA’s Mars Exploration Program portfolio. MAHLI was built by Malin Space Science Systems in San Diego.
To learn more about Curiosity, visit:
science.nasa.gov/mission/msl-curiosity
