On the origin of noctilucent clouds: Extraterrestrial dust and trapped water molecules

Abstract

Estimates of the seasonal variations of the spatial distribution of mesospheric dust of extraterrestrial origin have been made by analyzing the expected meridional trajectories of incoming extraterrestrial dust particles. High-latitude summer conditions are of particular interest because of the expected relation between the presence of mesospheric dust and visual observations of noctilucent clouds. The predicted spatial distribution of the incoming extraterrestrial dust is germane to a mechanism proposed for the formation of noctilucent clouds whereby the settling dust nuclei effectively act to sweep down the condensable water to provide a substantial enrichment of the moisture content at altitudes where noctilucent clouds are formed.