Space shower

 作者:凌新蹿     |      日期:2019-03-08 03:08:00
DUST from meteors could explain a mysterious layer of water vapour that hangs 70 kilometres above the tropics. Ultraviolet light destroys water molecules at altitudes above 60 kilometres, so something must continually replenish this layer. A bombardment of small “snowball” comets was suggested as a possible cause, but there is little evidence for this controversial idea (“Not a snowball’s chance…”, New Scientist, 12 July 1997, p 24). Now Michael Summers and David Siskind of the Naval Research Laboratory in Washington DC suggest that the water is formed by reactions on the surface of the dust particles created as meteors pass through the atmosphere ( Geophysical Research Letters, vol 26,