T his was the most forbidding landscape Saskia had ever seen. The Sahara might be even bigger and more arid, but it looked soft—a world of dunes. This was a world of rocks. Rocks that had never been rounded and smoothed by water. What little rain fell on it seemed to have been sucked up by plants with no purpose other than to produce spines and serrations. She gazed out the train’s window for hours without seeing a trace of surface water. Even before global warming, this landscape would kill anyone who tried to walk out of it.