Contents

10 February 1989
Vol 243, Issue 4892

About The Cover

A cross section through Earth's atmosphere over the Pacific Ocean, from the Space Shuttle Challenger. Stratosphere is in blue, troposphere in white and pink. This low sun angle photograph was taken by Bob Crippen, STS-17 Mission Commander, on 10 October 1984 from an altitude of 123 nautical miles. See page 745. [NASA Earth photographs are available from EROS Data Center, Sioux Falls, SD 57198; provided by M. R. Helfert, Code SN15, NASA-Johnson Space Center, Houston, TX 77058]