| 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.
|
