Researchers have solved the mystery of 4 million square miles of dark region in the northern lowlands in Mars: the dark areas of the Red Planet are made from glass.
Briony Horgan and Jim Bell of Arizona State University in Tempe analysed near-infrared spectra of the regions, gathered by the Mars Express orbiter. They found absorption bands characteristic of the iron in volcanic glass, a shiny substance similar to obsidian that forms when magma cools too fast for its minerals to crystallise.