Yellow surprise on Mars: NASA’s Curiosity rover finds rare sulfur crystals

Mars exploration just got a whole lot more exciting. NASA’s Curiosity rover discovered bright yellow sulfur crystals on Mars, which have never been observed before.

The surprise discovery of pure sulfur came from rocks within Gediz Vallis, a valley that runs through the side of Mount Sharp.

Curiosity has been climbing this 3-mile-tall (5-kilometer-tall) Martian mountain since 2014 — with each layer revealing secrets of the Red Planet’s watery past.

Finding yellow crystals

The yellow crystals were spotted while the rover explored a region rich in sulfur-based minerals called sulfates. These minerals occur as water evaporates, leaving sulfur behind.

This find is a complete surprise, as the conditions needed for its formation are unlike anything previously associated with this Martian location.

In the past, the rover discovered sulfur-containing rocks, but they were usually mixed with other materials. This time, Curiosity cracked open a rock and found it to be entirely made of pure sulfur. Scientists aren’t sure how this pure sulfur is connected to the other sulfur-containing rocks nearby.

In fact, Curiosity found a treasure trove of bright crystals in the area. The planetary scientists are baffled by the presence of such a vast field of pure sulfur.

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

Water’s lasting mark

This discovery is just one of many exciting finds Curiosity has made while exploring the Gediz Vallis channel since early 2024.

NASA is piecing together the history of the Gediz Vallis channel by examining the rocks found in the region. Smooth, rounded stones tell the tale of water flows, shaped like pebbles in a river. On the other hand, the presence of jagged, angular rocks within the debris mounds suggests they were dumped there by dry landslides rather than water .

The latest evidence suggests that both floods and landslides shaped the huge debris piles discovered there.

The rover data also shows that “water soaked into all the material that settled here.” According to the press release, water left an imprint on these rocks.

Chemical reactions triggered by the water etched white “halo” shapes into some of the rocks. Over time, relentless wind and sand exposure have gradually exposed these halo structures.

“This was not a quiet period on Mars. There was an exciting amount of activity here. We’re looking at multiple flows down the channel, including energetic floods and boulder-rich flows,” said Becky Williams, a scientist with the Planetary Science Institute in Tucson, Arizona, and the deputy principal investigator of Curiosity’s Mast Camera, or Mastcam.

Curiosity ‘s adventure began in 2011, and its mission is like a trip back in time.

It’s searching for clues in the Martian landscape where ancient environments might have held the key ingredients for microbial life to thrive — if it ever existed. With each surprising discovery, the curiosity about the Red Planet’s history grows. The continuous exploration and upcoming missions may ultimately reveal if it is a potentially life-supporting world, or not.