Mars is undergoing global warming that could profoundly change the planet’s climate in a few thousand years, new data suggests. High-resolution images taken by NASA’s Mars Global Surveyor show that the permanent south polar “ice” cap shrank significantly between two successive Martian summers – a period roughly corresponding to two Earth years. If the trend continues at the same rate and the polar cap is entirely frozen carbon dioxide, “the whole cap would be evaporated in a few thousand years,” Mike Caplinger of Malin Space Science Systems told New Scientist. This would release enough carbon dioxide to give Mars an atmosphere one-tenth the density of the Earth’s. “That takes us from a situation of working in a near vacuum with a space suit to being able to run around on the surface with an oxygen mask and a heavy coat. It’s what the terraforming people were always talking about,” says Caplinger.