NASA's Curiosity rover has sent back images of honeycomb-like textures called polygonal fractures, each one about 1.5 to 3 inches (4 to 8 centimeters) across. NASA reports:
The mission has spotted small patches of these geometric shapes several times before, but nothing at the scale discovered in Valle Grande. In a 360-degree panorama that the rover captured on June 19 and 20, the 4,930th and 4,931st Martian days, or sols, of the mission, the polygonal shapes spread in all directions for as far as the rover can see... "[T]his sea of polygons took our breath away," said the mission's project scientist, Ashwin Vasavada of NASA's Jet Propulsion Laboratory in Southern California... Some of the polygons that the mission has spotted in the past clearly formed as mud cracks, though a variety of processes can contribute to their honeycomb textures, including cycles of warm and cold temperatures or compression that squeezed water out of the sediment when the surface was buried.
These newly discovered polygons are among the many surprises Curiosity has trundled across since landing on Mars 14 years ago, on Aug. 5, 2012. Besides sulfur crystals, shiny meteorites, and other interesting geologic features, the rover has made major discoveries about the ancient Martian environment — most importantly, that it had the water, chemistry, and nutrients to support microbial life.
Billions of years ago, lakes and streams dappled the lower foothills of Mount Sharp, a 3-mile-tall (5-kilometer-tall) mountain that Curiosity has been ascending since 2014. The rover has previously uncovered chemistry left over from Mars' watery history, including carbon-based molecules believed to be precursors to RNA and DNA, two nucleic acids that carry genetic information. Scientists have no way of knowing whether these organic molecules were created by biologic or geologic processes — either path is possible — but their discovery reconfirmed that ancient Mars had the right chemistry to support life.
Dark, pebble-sized rocks also litter the area, NASA writes in a blog post, saying it's a "still-to-be-resolved question" as to whether they're bits of Mars that "floated" down from higher in the sediment layers, or "were ejected from distant impacts outside of Gale crater, or are meteorites from beyond Mars altogether."
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