Curiosity finds evidence of explosive volcanism on Mars

Los Angeles Times : While exploring Marias Pass in Gale Crater, Curiosity drilled into an area of rock that was curiously high in silicon and oxygen. An x-ray scattering analysis of the sample revealed that the rock contains the mineral tridymite, which had not previously been found on Mars. On Earth, tridymite is formed from the high temperatures and low pressures associated with violent volcanic explosions, such as the famous Mount St Helens eruption in 1980. It would be surprising if a similar type of eruption took place on Mars because all previous evidence of volcanism suggests eruptions resembling the steady flows of the Hawaiian island volcanoes. Explosive volcanoes are also primarily associated with plate tectonics, for which there has been no other evidence found on Mars. It’s unclear how the tridymite formed and how it ended up in sedimentary rock at unusually high concentrations.