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A HUGE cloud of particles that hung in the stratosphere over San Francisco
Bay for several days in April 1997 baffled scientists, but now NASA researchers
say they have solved the mystery of its origin. The 11,000-square-kilometre
cloud was originally spotted by a high-altitude aircraft flying at 70,000 feet.
Paul Newman of NASA’s Goddard Space Flight Center analysed global wind patterns
and data on cloud particles collected by the aircraft. He concluded the cloud
was actually a kerosene plume from a Russian rocket launched from the Baikonur
cosmodrome in Kazakhstan two weeks earlier (Geophysical Research
Letters, vol 28, p 959). Newman says he is surprised the cloud travelled so
far, and suggests more studies are needed into the environmental impact of such
plumes.