Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

A search for life on Earth from the Galileo spacecraft


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

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Carlson, R. W. et al. Space Sci. Rev. 60, 457–502 (1992).

    ADS  Article  Google Scholar 

  2. 2

    Hord, C. W. et al. Space Sci. Rev. 60, 503–530 (1992).

    ADS  Article  Google Scholar 

  3. 3

    Belton, M. J. S. et al. Space Sci. Rev. 60, 413–455 (1992).

    ADS  Article  Google Scholar 

  4. 4

    Gurnett, D. A. et al. Space Sci. Rev. 60, 341–355 (1992).

    ADS  Article  Google Scholar 

  5. 5

    Lederberg, J. Nature 207, 9–13 (1965).

    ADS  CAS  Article  Google Scholar 

  6. 6

    Lovelock, J. Nature 207, 568–570 (1965).

    ADS  CAS  Article  Google Scholar 

  7. 7

    Lovelock, J. E. Proc. R. Soc. B189, 167–181 (1975).

    ADS  CAS  Google Scholar 

  8. 8

    Sagan, C. Proc. R. Soc. B189, 143–166 (1975).

    ADS  Google Scholar 

  9. 9

    Carlson, R. W., Arakelian, T. & Smythe, W. D. Antarct. J. U.S. (in the press).

  10. 10

    Drossart, P. J. et al. Planet. Space Sci. (submitted).

  11. 11

    Henderson, L. J. The Fitness of the Environment: An Inquiry into the Biological Significance of the Properties of Matter (Peter Smith, Gloucester, Mass., 1913).

    Google Scholar 

  12. 12

    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).

    Google Scholar 

  13. 13

    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).

    Google Scholar 

  14. 14

    Walker, J. G. C. Evolution of the Atmosphere (Macmillan, New York, 1977).

    Google Scholar 

  15. 15

    Léger, A., Pirre, M. & Marceau, F. J. Astr. Astrophys. (in the press).

  16. 16

    Lippincott, E. R., Eck, R. V., Dayhoff, M. O. & Sagan, C. Astrophys. J. 147, 753–764 (1967).

    ADS  Article  Google Scholar 

  17. 17

    Chameides, W. L. & Davis, D. D. Chem. Engng. News 60, 38–52 (1992).

    Google Scholar 

  18. 18

    Hogan, K. B., Hoffman, J. S. & Thompson, A. M. Nature 354, 181–182 (1991).

    ADS  Article  Google Scholar 

  19. 19

    Lewis, J. S. & Prinn, R. G. Planets and Their Atmospheres (Academic, New York, 1984).

    Google Scholar 

  20. 20

    Bowker, D. E., Davis, R. E., Myrick, D. L., Stacy, K. & Jones, W. T. Ref. Publ. No. 1139 (NASA, Washington, 1985).

  21. 21

    Kilston, S. D., Drummond, R. R. & Sagan, C. Icarus 5, 79–98 (1966).

    ADS  Article  Google Scholar 

  22. 22

    Sagan, C. & Wallace, D. Icarus 15, 515–554 (1971).

    ADS  Article  Google Scholar 

  23. 23

    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).

    Google Scholar 

  24. 24

    Shklovskii, I. S. & Sagan, C. Intelligent Life in the Universe (Holden Day, San Francisco, 1966).

    Google Scholar 

  25. 25

    Sullivan, W. T., Brown, S. & Wetherill, C. Science 199, 377–388 (1978).

    ADS  Article  Google Scholar 

  26. 26

    Chapman, S. Proc. phys. Soc. 43, 483–501 (1931).

    ADS  Article  Google Scholar 

  27. 27

    Fainberg, J. & Stone, R. G. Space Sci. Rev. 16, 145–188 (1974).

    ADS  Article  Google Scholar 

  28. 28

    Gurnett, D. A. J. geophys. Res. 79, 4227–4238 (1974).

    ADS  Article  Google Scholar 

  29. 29

    LaBelle, J., Trumann, R. A., Boehm, M. H. & Gewecke, K. Radio Sci. 24, 725–737 (1989).

    ADS  Article  Google Scholar 

  30. 30

    Keller, A. thesis, Univ. Iowa (1990).

  31. 31

    Hines, C. O., Paghis, I., Hartz, T. R. & Fejer, J. A. Physics of the Earth's Upper Atmosphere (Prentice Hall, Englewood Cliffs, 1965).

    Google Scholar 

  32. 32

    Lederberg, J. & Sagan, C. Proc. Natn. Acad. Sci. U.S.A. 48, 1473–1475 (1962).

    ADS  CAS  Article  Google Scholar 

  33. 33

    Gold, T. Proc. natn. Acad. Sci. USA. 89, 6045–6049 (1992).

    ADS  CAS  Article  Google Scholar 

  34. 34

    Owen, T. in Strategies for the Search for Life in the Universe (ed. Papagiannis, M.) 177–185 (Reidel, Dordrecht, 1980).

    Book  Google Scholar 

Download references

Author information



Rights and permissions

Reprints 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).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links