Curiosity Rover Found a Martian Valley Cracked Into a Honeycomb of Palm-Sized Tiles
Picture a plain of cracked ground running to the horizon, the whole surface broken into a honeycomb of small tiles, each about the size of your palm, the pattern reaching as far as the eye can follow. That is the view NASA’s Curiosity rover sent home from a valley on Mars.
The rover started up that valley, nicknamed Valle Grande, a short while ago. What it drove into was a landscape stitched together from geometric shapes that scientists call polygonal fractures, each one roughly 1.5 to 3 inches across, about 4 to 8 centimeters. Curiosity has come across polygons on Mars before, in small patches. It had never seen a whole valley of them.
On June 19 and 20, its 4,930th and 4,931st Martian days, or sols, the rover built a 360-degree panorama of the place. In it, the tiles run to the edge of what the cameras can capture. The tiling even climbs the flanks of a nearby butte the team nicknamed Miraflores, a 20-foot rise whose top wears a deep layer of sand.
Ashwin Vasavada is the mission’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California, the lab that built Curiosity and runs it for NASA under Caltech’s management. He has watched a lot of Martian ground scroll past over the years. This view stopped him.
“We’ve seen a lot of fascinating landscapes through Curiosity’s eyes, but this sea of polygons took our breath away,” he said.
So what breaks a whole valley floor into tiles like this? The team is not saying yet. In the smaller patches Curiosity found earlier, the cause was clear enough: drying mud, the kind of cracking that opens when wet ground dries and shrinks. Several other processes can carve the same honeycomb, though. Repeated swings between warm and cold can do it. So can compression, the slow squeeze that pushes water out of sediment after it gets buried under more material.
Which of those shaped Valle Grande is the question the scientists are working through now. “We measured their shapes and chemistry carefully and are hopeful there are clues in the data as to how these features formed,” Vasavada said.
Curiosity is built for that kind of patient reading. It landed on Mars on August 5, 2012, and across 14 years it has turned up sulfur crystals, shiny meteorites, and the discovery that mattered most, evidence that ancient Mars once held the water, chemistry, and nutrients that could have supported microbial life.
Since 2014 the rover has been climbing Mount Sharp, a mountain about 3 miles tall. Its lower foothills once held lakes and streams, billions of years back. Somewhere on those slopes Curiosity found carbon-based molecules thought to be building blocks for RNA and DNA. No one can say whether biology or geology assembled them, since either is possible, and the find confirmed again that the chemistry for life was here.
The polygons are the newest entry in that long investigation. For now they are shapes and measurements, a valley of tiles waiting for the data to explain them. The rover keeps climbing, and the team keeps reading what it sends home.
