Enigmatic clouds illuminated

摘要

New findings from the edge of space are unmasking Earth's highest clouds.rnA NASA satellite called Aeronomy of Ice in the Mesosphere (AIM) is sending back the first detailed information on the 'noctilucent' clouds, which shimmer overhead just after sundown at high latitudes, where they reflect the below-horizon Sun.rnThe AIM data reveal that the clouds are ten times brighter than previously thought, and form at a broader range of altitudes. Although it had been thought that the clouds were limited to a single altitude band of 82 kilometres, in fact they can form at anywhere between 79 and 90 kilometres. AIM has also shown that small patchy groupings of cloud can grow dramatically with even a tiny fall in temperature.