11. Noctilucent clouds were first detected from space by an instrument on the OGO-6 satellite in 1972.12. One theory holds that lofty noctilucent clouds form when water from disintegrated meteorites freezes onto meteoric dust. 13. On Wednesday night, the weather observer at Winnipeg, Manitoba, noted the relatively rare sighting of noctilucent clouds . 14. Like noctilucent clouds on Earth, they can be observed only when the Sun is below the horizon. 15. Noctilucent clouds are located in the mesosphere.16. Noctilucent clouds are generally colourless or pale blue, although occasionally other colours including red and green occur.17. They compared the noctilucent cloud phenomenon to the exhaust plume from NASA's " Endeavour " space shuttle. 18. The characteristic blue colour comes from absorption by ozone in the path of the sunlight illuminating the noctilucent cloud . 19. During his life he played a leading role in supporting amateurs in observations of noctilucent clouds , aurorae, and nightglow. 20. Ultraviolet radiation from the Sun breaks water molecules apart, reducing the amount of water available to form noctilucent clouds .
