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 search for extraterrestrial life by modern interplanetary spacecraft.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Carlson, R. W. et al. Space Sci. Rev. 60, 457–502 (1992).
Hord, C. W. et al. Space Sci. Rev. 60, 503–530 (1992).
Belton, M. J. S. et al. Space Sci. Rev. 60, 413–455 (1992).
Gurnett, D. A. et al. Space Sci. Rev. 60, 341–355 (1992).
Lederberg, J. Nature 207, 9–13 (1965).
Lovelock, J. Nature 207, 568–570 (1965).
Lovelock, J. E. Proc. R. Soc. B189, 167–181 (1975).
Sagan, C. Proc. R. Soc. B189, 143–166 (1975).
Carlson, R. W., Arakelian, T. & Smythe, W. D. Antarct. J. U.S. (in the press).
Drossart, P. J. et al. Planet. Space Sci. (submitted).
Henderson, L. J. The Fitness of the Environment: An Inquiry into the Biological Significance of the Properties of Matter (Peter Smith, Gloucester, Mass., 1913).
von Zahn, U., Kumar, R. S., Neimann, H. & Prinn, R. in Venus Ch. 13 (eds Hunten, D. M., Colin, L., Donahue, T. M. & Moroz, V. I.) (Univ. of Arizona Press, Tucson, 1983).
Owen, T. in Mars Ch. 25 (eds Keiffer, H. H., Jakosky, B. M., Snyder, C. W. & Matthews, M. S.) (Univ. of Arizona Press, Tucson, 1992).
Walker, J. G. C. Evolution of the Atmosphere (Macmillan, New York, 1977).
Léger, A., Pirre, M. & Marceau, F. J. Astr. Astrophys. (in the press).
Lippincott, E. R., Eck, R. V., Dayhoff, M. O. & Sagan, C. Astrophys. J. 147, 753–764 (1967).
Chameides, W. L. & Davis, D. D. Chem. Engng. News 60, 38–52 (1992).
Hogan, K. B., Hoffman, J. S. & Thompson, A. M. Nature 354, 181–182 (1991).
Lewis, J. S. & Prinn, R. G. Planets and Their Atmospheres (Academic, New York, 1984).
Bowker, D. E., Davis, R. E., Myrick, D. L., Stacy, K. & Jones, W. T. Ref. Publ. No. 1139 (NASA, Washington, 1985).
Kilston, S. D., Drummond, R. R. & Sagan, C. Icarus 5, 79–98 (1966).
Sagan, C. & Wallace, D. Icarus 15, 515–554 (1971).
Sagan, C. et al. in Biology and the Exploration of Mars Ch. 9 (eds Pittendrigh, C. S., Vishniac, W. & Pearman, J. P. T.) (Natn. Acad. Sci. Washington, 1966).
Shklovskii, I. S. & Sagan, C. Intelligent Life in the Universe (Holden Day, San Francisco, 1966).
Sullivan, W. T., Brown, S. & Wetherill, C. Science 199, 377–388 (1978).
Chapman, S. Proc. phys. Soc. 43, 483–501 (1931).
Fainberg, J. & Stone, R. G. Space Sci. Rev. 16, 145–188 (1974).
Gurnett, D. A. J. geophys. Res. 79, 4227–4238 (1974).
LaBelle, J., Trumann, R. A., Boehm, M. H. & Gewecke, K. Radio Sci. 24, 725–737 (1989).
Keller, A. thesis, Univ. Iowa (1990).
Hines, C. O., Paghis, I., Hartz, T. R. & Fejer, J. A. Physics of the Earth's Upper Atmosphere (Prentice Hall, Englewood Cliffs, 1965).
Lederberg, J. & Sagan, C. Proc. Natn. Acad. Sci. U.S.A. 48, 1473–1475 (1962).
Gold, T. Proc. natn. Acad. Sci. USA. 89, 6045–6049 (1992).
Owen, T. in Strategies for the Search for Life in the Universe (ed. Papagiannis, M.) 177–185 (Reidel, Dordrecht, 1980).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Sagan, C., Thompson, W., Carlson, R. et al. A search for life on Earth from the Galileo spacecraft. Nature 365, 715–721 (1993). https://doi.org/10.1038/365715a0
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1038/365715a0
- Springer Nature Limited
This article is cited by
-
How would we know whether there is life on Earth? This bold experiment found out
Nature (2023)
-
Atmospheric carbon depletion as a tracer of water oceans and biomass on temperate terrestrial exoplanets
Nature Astronomy (2023)
-
Understanding planetary context to enable life detection on exoplanets and test the Copernican principle
Nature Astronomy (2022)
-
On the Habitability and Future Exploration of Ocean Worlds
Space Science Reviews (2020)
-
Future Missions Related to the Determination of the Elemental and Isotopic Composition of Earth, Moon and the Terrestrial Planets
Space Science Reviews (2020)