NASA’s Curiosity rover has made remarkable discoveries on Mars, revealing the Red Planet once had a dynamic and water-rich environment.

Curiosity made a groundbreaking find in May. While traversing the Martian surface, the rover’s wheels crushed a seemingly ordinary rock, revealing bright yellow sulfur crystals. This marks the first time pure elemental sulfur has been found on Mars, leaving scientists both excited and puzzled.

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

The sulfur discovery is among several significant findings made by Curiosity as it explores the Gediz Vallis channel on Mount Sharp. The three-mile-tall mountain has been the rover’s exploration site since 2014, with each rock layer offering insights into Mars’ past.

The channel itself, identified from orbit years before Curiosity’s landing, was a key reason for choosing this region for exploration. Scientists believed it holds clues to Mars’ watery history, and recent discoveries have proven them correct.

While navigating the channel, Curiosity encountered large debris mounds. Initially, scientists were unsure if these were remnants of ancient floods or landslides. Close-up examinations by the rover revealed that both processes likely shaped the dramatic landscape.

Some debris piles contain rounded rocks, similar to those in Earth’s riverbeds, indicating they were shaped by flowing water. Others have angular stones, suggesting they resulted from dry avalanches. This combination of water-worn and freshly broken rocks suggests a dynamic, changing Mars.

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