title: A search for life on Earth from the Galileo spacecraft.
abstract: In its December 1990 fly-by of Earth, the Galileo spacecraft found evidence of abundant gaseous oxygen, a widely distributed surface pigment with a sharp absorption edge in the red part of the visible spectrum, and atmospheric methane in extreme thermodynamic disequilibrium; together, these are strongly suggestive of life on Earth.  Moreover, the presence of narrow-band, pulsed, amplitude-modulated radio transmission seems uniquely attributable to intelligence.  These observations constitute a control experiment for the serach for extraterrestrial life by modern interplanetary spacecraft.
authors.affiliation: Laboratory for Planetary Studies, Cornell University, Ithaca, New York 14853, USA.
authors.forename: C
authors.initials: C
authors.lastname: Sagan
authors.forename: W R
authors.initials: WR
authors.lastname: Thompson
authors.forename: R
authors.initials: R
authors.lastname: Carlson
authors.forename: D
authors.initials: D
authors.lastname: Gurnett
authors.forename: C
authors.initials: C
authors.lastname: Hord
mesh_terms: D001272:Atmosphere; D018534:Earth, Planet; D018559:Exobiology; D005118:Extraterrestrial Environment; D008697:Methane / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D011846:Radio Waves; D013026:Space Flight; D018531:Spacecraft; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D014867:Water
chemical_list: D014867:Water; D008697:Methane; D010100:Oxygen