findings. DAN's high neutron readings would normally have been interpreted as meaning the region was hydrogen-rich, and ChemCam's high-silica readings were not surprising given the ubiquity of silica-rich deposits on Mars, but taken together it was clear that further study of the region was needed. Following conjunction, NASA directed the Curiosity rover back to the area where the readings had been taken and discovered that large amounts of tridymite were present. How they were formed remains a mystery. See also Cristobalite Coesite Stishovite References External links Mineral galleries Standard pressure polymorphs of SiO2 Study: Explosive volcanic eruption produced rare mineral on Mars Orthorhombic minerals Minerals in space group 20 Industrial minerals Silica polymorphs Silicon dioxide