Nature 385, 234 - 236 (16 January 1997); doi:10.1038/385234a0

Habitable moons around extrasolar giant planets

Darren M. Williams^*, James F. Kasting^† & Richard A. Wade^*

^*Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, Pennsylvania 16802, USA
^†Department of Geosciences, The Pennsylvania State University, 211 Deike Building, University Park, Pennsylvania 16802, USA

Possible planetary objects have now been discovered^1–9 orbiting nine different main-sequence stars. These companion objects (some of which might actually be brown dwarfs) all have a mass at least half that of Jupiter, and are therefore unlikely to be hospitable to Earth-like life: jovian planets and brown dwarfs support neither a solid nor a liquid surface near which organisms might dwell. Here we argue that rocky moons orbiting these companions could be habitable if the planet–moon system orbits the parent star within the so-called 'habitable zone'¹⁰, where life-supporting liquid water¹¹ could be present. The companions to the stars 16 Cygni B and 47 Ursae Majoris might satisfy this criterion. Such a moon would, however, need to be large enough (>0.12 Earth masses) to retain a substantial and long-lived atmosphere, and would also need to possess a strong magnetic field in order to prevent its atmosphere from being sputtered away by the constant bombardment of energetic ions from the planet's magnetosphere.

1. Mayor, M. & Queloz, D. Nature 378, 355−359 (1995). | Article | ISI | ChemPort |
2. Marcy, G. W. & Butler, R. P. Astrophys. J. 464, L147−L151 (1996). | Article | ISI |
3. Butler, R. P. & Marcy, G. W. Astrophys. J. 464, L153−L156 (1996). | Article | ISI |
4. Gatewood, G. Bull. Am. Astron. Soc. 28, 885 (1996).
5. Butler, R. P., Marcy, G. W., Williams, E., Hauser, H. & Shirts, P. Astrophys. J. (submitted).
6. Latham, D. W., Mazeh, T., Stefanik, R. P., Mayor, M. & Burki, G. Nature 339, 38−40 (1989). | Article | ISI |
7. Cochran, W. D., Hatzes, A. P., Butler, R. P. & Marcy, G. W. Bull. Am. Astron. Soc. 28, 1111 (1996).
8. Marcy, G. W., Butler, R. P., Williams, E., Bildsten, L. & Graham, J. R. Astrophys. J. (submitted).
9. Cochran, W. D., Hatzes, A. P. & Hancock, T. J. Astrophys. J. 380, L35−L38 (1991). | Article |
10. Kasting, J. F., Whitmire, D. P. & Reynolds, R. T. Icarus 101, 1−21 (1993). | Article |
11. Brack, A. Orig. Life 23, 3−10 (1993). | ChemPort |
12. Chyba, C. F. Nature 343, 129−133 (1990). | Article |
13. Lin, D., Bodenheimer, P. & Richardson, D. C. Nature 380, 606−607 (1996). | Article | ISI | ChemPort |
14. Griffith, C. A. & Zahnle, K. J. Geophys. Res. 100, 16907−16922 (1995). | Article | PubMed | ChemPort |
15. Prinn, R. G. & Fegley, B. Astrophys. J. 249, 308−317 (1981). | Article | ISI | ChemPort |
16. Watson, A., Lovelock, J. E. & Margulis, L. Biosystems 10, 293−298 (1978). | Article | PubMed | ISI | ChemPort |
17. McKay, C. P., Toon, O. B. & Kasting, J. F. Nature 352, 489−496 (1991). | Article | PubMed | ChemPort |
18. McElroy, M. B. Science 175, 443−445 (1972). | ChemPort |
19. Fox, J. L. J. Geophys. Res. 98, 3297−3310 (1993). | ChemPort |
20. Strobel, D. F., Summers, M. E. & Zhu, X. Icarus 100, 512−526 (1992). | Article | ChemPort |
21. Van Allen, J. A. in Jupiter (ed. Gehrels, T.) (Univ. Arizona Press, Tucson, 1976).
22. Kass, D. M. & Yung, Y. L. Science 268, 697−699 (1995). | PubMed | ChemPort |
23. Kivelson, M. G. et al. Nature 384, 537−541 (1996). | Article | ISI | ChemPort |
24. Gurnett, D. A., Kurtin, W. S., Rowe, A., Bolton, S. J. & Kennel, C. F. Nature 384, 535−537 (1996). | Article | ChemPort |
25. Peale, S. J. in Planetary Satellites (ed. Burns, J. A.) 87−112 (Univ. Arizona Press, Tucson, 1977).
26. Boss, A. P. Nature 379, 397−398 (1996). | Article | ChemPort |
27. Saumon, D. et al. Astrophys. J. 460, 993−1018 (1996). | Article | ChemPort |
28. Walker, J. C. G., Hays, P. B. & Kasting, J. F. J. Geophys. Res. 86, 9776−9782 (1981). | ISI | ChemPort |
29. Kasting, J. F., Toon, O. B. & Pollack, J. B. Sci. Am. 256, 90−97 (1988). | PubMed | ChemPort |
30. Turcotte, D. L. J. Geophys. Res. 101, 4765−4773 (1996). | Article |
31. Turcotte, D. L. & Schubert, G. Geodynamics: Applications of Continuum Physics to Geologic Problems 137−139 Wiley, New York, 1982).
32. Solomon, S. C. & Head, J. W. J. Geophys. Res. 95, 11073−11083 (1990). | ISI |
33. Francis, P. W. & Wood, C. A. J. Geophys. Res. 87, 9881−9889 (1982).
34. Peale, S. J., Cassen, P. & Reynolds, R. T. Science 203, 892−894 (1979). | ISI |
35. Roy, A. E. Orbital Motion 3rd edn 239−279 (Hilger, Philadelphia, 1988).
36. Rasio, F. A. & Ford, E. B. Science 274, 954−956 (1996). | Article | PubMed | ISI | ChemPort |