September 29, 2008
An explanation for a strange property of night-shining clouds has been proposed by Paul Bellan, Professor of Applied Physics. Noctilucent clouds - thin, wispy electric blue clouds clouds hovering at 85 km altitude - are highly reflective to radar. Ice grains in noctilucent clouds are coated with a thin film of metal, made of sodium and iron. The metal film causes radar waves to reflect off ripples in the cloud in a manner analogous to how x-rays reflect from a crystal lattice. [Caltech Press Release]