Mars has thrown Curiosity another strange patch of ground.
NASA says the rover has entered a valley nicknamed Valle Grande, where the surface is covered in honeycomb-like polygonal fractures measuring about 4 to 8 centimetres across. Curiosity has seen small clusters of similar geometric shapes before, but NASA said it has never seen anything close to the scale of the field now visible in Valle Grande.
The full extent of the formations appears in a 360-degree panorama captured on June 19 and 20, during the 4,930th and 4,931st Martian days, or sols, of the mission. The polygons stretch across the terrain in every direction, as far as the rover can see.
The patterns also climb the sides of a nearby butte nicknamed Miraflores. The formation rises 6 metres above the surrounding area and is capped by a thick layer of sand.
“We’ve seen a lot of fascinating landscapes through Curiosity’s eyes, but this sea of polygons took our breath away,” said the mission’s project scientist, Ashwin Vasavada of NASA’s Jet Propulsion Laboratory in Southern California. “We measured their shapes and chemistry carefully and are hopeful there are clues in the data as to how these features formed.”
Some polygonal formations previously examined by Curiosity clearly began as cracks in drying mud. NASA said several different processes can produce this kind of honeycomb appearance.
Repeated warming and cooling can fracture the ground into geometric shapes. Compression may also create similar patterns by forcing water out of sediment after the material becomes buried beneath the surface.
Scientists are now studying the newly found formations to work out which of those processes, or what combination of them, shaped the landscape in Valle Grande.
The polygon field is the latest in a long series of discoveries made by Curiosity since it landed on Mars on August 5, 2012. During the mission, the rover has encountered sulfur crystals, reflective meteorites and other unusual geologic features.
NASA said Curiosity has also changed scientists’ understanding of ancient Mars by showing the planet once had water, useful chemistry and nutrients that could have supported microbial life.
Billions of years ago, lakes and streams were scattered across the lower foothills of Mount Sharp, a mountain 5 kilometres tall that Curiosity has been climbing since 2014. The rover has found chemical traces from that wetter period, including carbon-based molecules believed to be precursors to RNA and DNA, two nucleic acids that carry genetic information.
Scientists cannot determine if those organic molecules were produced through biologic or geologic processes. NASA said both explanations remain possible.
Managed by Caltech in Pasadena, JPL built Curiosity and leads the mission on behalf of NASA’s Science Mission Directorate in Washington as part of the agency’s Mars Exploration Program portfolio.
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