Scientists were stunned when a rock broke off after NASA's Mars rover Curiosity passed over it, revealing something never before seen on the Red Planet: "yellow sulfur crystals."
Since October 2023, the rover has been exploring a region of Mars rich in sulfates, a type of salt containing sulfur that forms as water evaporates.
While sulfur had been discovered before, but only as components of sulfur-based minerals, that is, a mixture of sulfur and other substances, this time, the sulfur discovered was pure, the first of its kind.
It is not clear what relationship, if any, elemental (natural raw) sulfur has to other sulfur minerals in the area.
While people associate sulfur with the smell of rotten eggs (from hydrogen sulfide gas), elemental sulfur is odorless. Its formation requires specific conditions not previously associated with this Martian location. So the discovery of an entire field of shiny, sulfur-laden rocks is actually quite surprising.
Sulfur itself is not direct evidence of life, but its presence can provide important clues about past environmental conditions that may have been favorable for life.
Some sulfur formations on Earth are associated with biological activity, such as microorganisms, which can produce sulfur compounds during metabolism.
“Finding a field of rocks made of pure sulfur is like finding an oasis in the desert,” said Ashwin Vasavada, Curiosity’s project scientist from NASA’s Jet Propulsion Laboratory in Southern California. “It shouldn’t be there, so now we have to explain it. Finding strange and unexpected things is what makes planetary exploration so exciting.”
This latest discovery is one of many made by Curiosity while driving off-road inside the Gediz Vallis, a canyon that runs down a 3-mile (5-km) section of Mount Sharp.
Each layer of the mountain represents a different period in Mars' 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 it existed.
Scientists believe the channel was carved by flows of liquid water and debris that left a ridge of rock and sediment extending 2 miles down the mountainside in the channel’s interior. The goal is to develop a better understanding of how this landscape has changed over billions of years.
The crushed samples are now being closely examined to determine their composition, promising further insights into Mars’ mysterious geological history. Each new discovery brings us one step closer to understanding Mars’ history and whether it once harbored conditions suitable for life.
The discovery of sulfur on Mars enhances our understanding of our neighboring planet while igniting our curiosity about what else lies beyond. With each new step the rover takes, we learn more about the Red Planet in an attempt to answer the age-old question: “Was there life on Mars?”