During the Astro-1 [ http://antwrp.gsfc. ] astronomy mission of December, 1990, Space Shuttle [ http://spaceflight. ] astronauts photographed this stunning [ http://antwrp.gsfc. ] view of the setting full moon poised above the Earth's limb. In the foreground, towering clouds of condensing water vapor [ http://antwrp.gsfc. ] mark the extent of the troposphere, the lowest layer of the planet's life-sustaining atmosphere [ http://liftoff.msfc atmosphere.html ]. Strongly scattering blue sunlight, the upper atmospheric layer, the stratosphere, fades dramatically to the black background of space. Moon [ http://cass.jsc.nas ] and clouds are [ http://climate.gsfc Types/Types.htmd/TXT .html ] strong visual elements of many well known portraits of planet Earth [ http://earthobserva ], including Ansel Adams' famous "Moonrise, Hernandez, New Mexico" [ http://www.geh.org/ m197400820001_ful.ht ml#topofimage ], photographed in 1941.