“This shouldn’t be there”

NASA’s Curiosity rover deployed into the Jezero Crater on Mars captured this final image of a field of bright white sulfur rocks before leaving the so-called Gediz Valley Channel. It was here that the rover first discovered pure sulfur on Mars. Scientists are still not sure why these rocks formed here.

“Finding a field of pure sulfur rocks is like finding an oasis in the desert,” said Curiosity project scientist Ashwin Vasavada. “It shouldn’t be there, so now we have to explain it. Discovering strange and unexpected things is what makes planetary exploration so exciting.”

Images of the area taken earlier by NASA’s Mars Reconnaissance Orbiter (MRO) showed it was a light-colored area with nothing of note in it. It turns out that the sulfur rocks were too small to be seen by MRO’s High Resolution Image Survey (HiRISE), and the Curiosity team was intrigued by their discovery when the rover arrived in the area. They were even more surprised when Curiosity flew over one of the rocks and crushed it, revealing yellow crystals inside.

The rover’s scientific instruments confirmed that the rock was pure sulfur, something no mission on Mars had ever seen. The team has no immediate explanation for why the sulfur formed there; on Earth it is associated with volcanoes and hot springs, and at Mount Sharp there is no evidence to suggest any of these causes.

“We looked at the sulfur field from all sides, top and side, and looked for anything mixed with sulfur that could give us a clue as to how it formed. “We’ve collected a ton of data, and now we have a fun puzzle to solve,” Curiosity project scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory (JPL) said in a statement.

Curiosity, which has traveled some 33 kilometers since landing in 2012, is now moving along the western edge of the Gediz Valley channel, collecting several more panoramas to document the region before heading towards a box-shaped structure that, from orbit, looks like a network of spider webs spreading across surfaces.