NASA's Super Soaker mission was an extreme DIY project: To better understand how noctilucent, or night-shining, clouds form, researchers made one. One predawn morning in January 2018, researchers in Alaska launched a rocket hauling a bathtub's worth of water. When the rocket was 85 kilometers off the ground, its water cargo exploded, spraying the mesosphere with vapor that froze into a cloud of ice crystals. When such high-flying hazes of ice are illuminated by sunlight from beyond the horizon before sunrise or after sunset, they are seen in the dark sky as shimmery noctilucent clouds. In the experiment, reflections from a ground-based laser aimed at the rocket detected the ice crystals 18 seconds after the explosion. Computer simulations suggest that the only way the cloud could have formed so fast is if the vapor plume was about 25 degrees Celsius cooler than the surrounding air, researchers report in the February Journal of Geophysical Research: Space Physics.
展开▼
