A search for life on Earth from the Galileo spacecraft

• Published in: Nature (London) Vol. 365; no. 6448; pp. 715 - 721
• Main Authors: Sagan, C., Thompson, W. R., Carlson, R., Gurnett, D., Hord, C.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Nature Publishing 21.10.1993; Nature Publishing Group
• Subjects: Astronomical and space-research instrumentation; Astronomy; Atmosphere; Earth; Earth (Planet); Earth, ocean, space; Exact sciences and technology; Exobiology; Extraterrestrial Environment; Extraterrestrial life; Extraterrestrial life and intelligence; Fundamental astronomy and astrophysics. Instrumentation, techniques, and astronomical observations; Lunar, planetary, and deep-space probes; Methane - chemistry; Oxygen - chemistry; Radio Waves; Space exploration; Space Flight; Space life sciences; Spacecraft; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet; Water; Unmanned; Non-Nasa Center; Long Duration; Nasa Discipline Exobiology; Flight Experiment; Galileo Project; Flyby missions; Galileo space probes; ETI; Earth planet; NASA Discipline Exobiology; Non-NASA Center
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/365715a0

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.