Near Earth's north and south poles, wispy, iridescent clouds often shimmer high in the summertime sky around dusk and dawn. These night-shining, or noctilucent, clouds are sometimes spotted farther from the poles as well, at a rate that varies dramatically from year to year. According to a new study using NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite, which is managed by the Explorers Program Office at NASA's Goddard Space Flight Center in Greenbelt, Maryland, morning rocket launches are partly responsible for the appearance of the lower-latitude clouds.