NASA scientists say pure sulfur has been found on Mars for the first time after the Curiosity rover inadvertently uncovered a cluster of yellow crystals when it drove over a rock. And it looks like the area is filled with it. It's an unexpected discovery -- while minerals containing sulfur have been observed on the Red Planet, elemental sulfur on its own has never been seen there before. "It forms in only a narrow range of conditions that scientists haven't associated with the history of this location," according to NASA. Curiosity cracked open the rock on May 30 while driving in a region known as the Gediz Vallis channel, where similar rocks were seen all around.