NASA's Curiosity rover discovers a surprise in a Martian rock
Scientists were stunned on May 30 when a rock that NASA's Curiosity Mars rover drove over cracked open to reveal something never seen before on the Red Planet: yellow sulfur crystals.
Since October 2023, the rover has been exploring a region of Mars rich with sulfates, a kind of salt that contains sulfur and forms as water evaporates. But where past detections have been of sulfur-based minerals—in other words, a mix of sulfur and other materials—the rock Curiosity recently cracked open is made of elemental (pure) sulfur. It isn't clear what relationship, if any, the elemental sulfur has to other sulfur-based minerals in the area.
While people associate sulfur with the odor from rotten eggs (the result of hydrogen sulfide gas), elemental sulfur is odorless. It forms in only a narrow range of conditions that scientists haven't associated with the history of this location. And Curiosity found a lot of it—an entire field of bright rocks that look similar to the one the rover crushed.
"Finding a field of stones made of pure sulfur is like finding an oasis in the desert," said Curiosity's project scientist, Ashwin Vasavada of NASA's Jet Propulsion Laboratory in Southern California. "It shouldn't be there, so now we have to explain it. Discovering strange and unexpected things is what makes planetary exploration so exciting."
It's one of several discoveries Curiosity has made while off-roading within Gediz Vallis channel, a groove that winds down part of the 3-mile-tall (5-kilometer-tall) Mount Sharp, the base of which the rover has been ascending since 2014. Each layer of the mountain represents a different period of Martian history. Curiosity's mission is to study where and when the planet's ancient terrain could have provided the nutrients needed for microbial life, if any ever formed on Mars.
These yellow crystals were revealed after NASA's Curiosity happened to drive over a rock and crack it open on May 30. Using an instrument on the rover's arm, scientists later determined these crystals are elemental sulfur—and it's the first time this kind of sulfur has been found on the Red Planet. Credit: NASA/JPL-Caltech/MSSS
NASA’s Curiosity captured this close-up image of a rock nicknamed “Snow Lake” on June 8, 2024, the 4,209th Martian day, or sol, of the mission. Nine days earlier, the rover had crushed a similar-looking rock and revealed crystalline textures—and elemental sulfur—inside. Credit: NASA/JPL-Caltech/MSSS
NASA/JPL-Caltech/MSSS NASA’s Curiosity Mars rover captured this view of Gediz Vallis channel on March 31. This area was likely formed by large floods of water and debris that piled jumbles of rocks into mounds within the channel. Credit: NASA/JPL-Caltech/MSSS
While exploring Gediz Vallis channel in May, NASA’s Curiosity captured this image of rocks that show a pale color near their edges. These rings, also called halos, resemble markings seen on Earth when groundwater leaks into rocks along fractures, causing chemical reactions that change the color. Credit: NASA/JPL-Caltech/MSSS