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On the probability of habitable planets

Published online by Cambridge University Press:  15 May 2013

François Forget*
Laboratoire de Météorologie Dynamique, IPSL, CNRS, UPMC, Paris, France e-mail:


In the past 15 years, astronomers have revealed that a significant fraction of the stars should harbour planets and that it is likely that terrestrial planets are abundant in our galaxy. Among these planets, how many are habitable, i.e. suitable for life and its evolution? These questions have been discussed for years and we are slowly making progress. Liquid water remains the key criterion for habitability. It can exist in the interior of a variety of planetary bodies, but it is usually assumed that liquid water at the surface interacting with rocks and light is necessary for emergence of a life able to modify its environment and evolve. The first key issue is thus to understand the climatic conditions allowing surface liquid water assuming a suitable atmosphere. These have been studied with global mean one-dimensional (1D) models which have defined the ‘classical habitable zone’, the range of orbital distances within which worlds can maintain liquid water on their surfaces (Kasting et al. 1993). A new generation of 3D climate models based on universal equations and tested on bodies in the solar system are now available to explore with accuracy climate regimes that could locally allow liquid water. The second key issue is now to better understand the processes which control the composition and the evolution of the atmospheres of exoplanets, and in particular the geophysical feedbacks that seem to be necessary to maintain a continuously habitable climate. From that point of view, it is not impossible that the Earth's case may be special and uncommon.

Research Article
Copyright © Cambridge University Press 2013 

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Batalha, N.M. et al. (2011). Kepler's first rocky planet: Kepler-10b. Astrophys. J. 729, 27.Google Scholar
Beaulieu, J.-P. et al. (2006). Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing. Nature 439, 437440.CrossRefGoogle ScholarPubMed
Bonfils, X. et al. (2013). The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample. Astron. Astrophys. 549, A109.Google Scholar
Borucki, W.J. et al. (2011). Characteristics of planetary candidates observed by Kepler. II. Analysis of the first four months of data. Astrophys. J. 736, 19.Google Scholar
Borucki, W.J. et al. (2012). Kepler-22b: a 2.4 Earth-radius planet in the habitable zone of a Sun-like star. Astrophys. J. 745, 120.Google Scholar
Brack, A. (1993). Liquid water and the origin of life. Orig. Life 3–10, 23.Google Scholar
Buccino, A.P., Lemarchand, G.A. & Mauas, P.J.D. (2007). UV habitable zones around M stars. Icarus 192, 582587.Google Scholar
Carter, B. (2008). Five- or six-step scenario for evolution? Int. J. Astrobiol. 7, 177182.Google Scholar
Cassan, A. et al. (2012). One or more bound planets per Milky Way star from microlensing observations. Nature 481, 167169.Google Scholar
Cernicharo, J. & Crovisier, J. (2005). Water in space: the water world of ISO. Space Sci. Rev. 119, 2969.CrossRefGoogle Scholar
Charbonneau, D. et al. (2009). A super-Earth transiting a nearby low-mass star. Nature 462, 891894.CrossRefGoogle ScholarPubMed
Ehrenfreund, P., Spaans, M. & Holm, N.G. (2011). The evolution of organic matter in space. Philos. Trans. R. Soc. Lond. A 369, 538554.Google Scholar
Forget, F. & Pierrehumbert, R.T. (1997). Warming early Mars with carbon dioxide clouds that scatter infrared radiation. Science 278, 12731276.Google Scholar
Forget, F., Hourdin, F., Fournier, R., Hourdin, C., Talagrand, O., Collins, M., Lewis, S.R., Read, P.L. & Huot, J.-P. (1999). Improved general circulation models of the Martian atmosphere from the surface to above 80 km. J. Geophys. Res. 104, 24,15524,176.Google Scholar
Fressin, F., Torres, G., Charbonneau, D., Bryson, S.T., Christiansen, J., Dressing, C.D., Jenkins, J.M., Walkowicz, L.M. & Batalha, N.M. (2013). The false positive rate of Kepler and the occurrence of planets. Astrophys. J. 766, 81.Google Scholar
Gerard, J.-C., Hauglustaine, D.A. & Francois, L.M. (1992). The faint young sun climatic paradox: a simulation with an interactive seasonal climate-sea ice model. Paleogeogr. Paleoclimatol. Paleoecol. 97, 133150.Google Scholar
Henning, T. & Salama, F. (1998). Carbon in the Universe. Science 282, 22042206.Google Scholar
Hoffman, P.F., Kaufman, A.J., Halverson, G.P. & Schrag, D.P. (1998). A neoproterozoic snowball Earth. Science 281, 13421346.CrossRefGoogle ScholarPubMed
Hourdin, F., Le Van, P., Forget, F. & Talagrand, O. (1993). Meteorological variability and the annual surface pressure cycle on Mars. J. Atmos. Sci. 50, 36253640.2.0.CO;2>CrossRefGoogle Scholar
Hourdin, F., Talagrand, O., Sadourny, R., Regis, C., Gautier, D. & McKay, C.P. (1995). General circulation of the atmosphere of Titan. Icarus 117, 358374.Google Scholar
Howard, A.W., Marcy, G.W., Johnson, J.A., Fischer, D.A., Wright, J.T., Isaacson, H., Valenti, J.A., Anderson, J., Lin, D.N.C. & Ida, S. (2010). The occurrence and mass distribution of close-in super-Earths, Neptunes, and Jupiters. Science 330, 653655.Google Scholar
Joshi, M. (2003). Climate model studies of synchronously rotating planets. Astrobiology 3, 415427.Google Scholar
Kaltenegger, L., Traub, W.A. & Jucks, K.W. (2007). Spectral evolution of an earth-like planet. Astrophys. J. 658, 598616.Google Scholar
Kaltenegger, L., Segura, A. & Mohanty, S. (2011). Model spectra of the first potentially habitable super-Earth Gl581d. Astrophys. J. 733, 35.Google Scholar
Kaltenegger, L. & Selsis, F. (2007). Biomarkers set in context, in Extrasolar Planets. Dvorak, R. (ed), pp. 7598. Wiley-VCH, Berlin.Google Scholar
Kasting, J.F. (1988). Runaway and moist greenhouse atmosphere and the evolution of Earth and Venus. Icarus 74, 472494.Google Scholar
Kasting, J.F. (1997). Warming early Earth and Mars. Science 276, 12131215.CrossRefGoogle ScholarPubMed
Kasting, J.F., Whitmire, D.P. & Reynolds, R.T. (1993). Habitable zones around main sequence stars. Icarus 101, 108128.CrossRefGoogle ScholarPubMed
Kasting, J.F. (2001). Essay Review: P. Ward and D. Brownlee's “Rare Earth”. Perspective in biology and Medecine 44, 117131.Google Scholar
Korenaga, J. (2010). On the likelihood of plate tectonics on super-Earths: does size matter? Astrophys. J. 725, L43L46.Google Scholar
Lammer, H. et al. (2009). What makes a planet habitable? Astron. Astrophys. Rev. 17, 181249.Google Scholar
Lammer, H., Kislyakova, K.G., Odert, P., Leitzinger, M., Schwarz, R., Pilat-Lohinger, E., Kulikov, Y.N., Khodachenko, M.L., Güudel, M. & Hanslmeier, A. (2011). Pathways to earth-like atmospheres. Extreme ultraviolet (EUV)-powered escape of hydrogen-rich protoatmospheres. Orig. Life Evol. Biosph. 41, 503522.Google Scholar
Lebonnois, S., Hourdin, F., Eymet, V., Crespin, A., Fournier, R. & Forget, F. (2010). Superrotation of Venus’ atmosphere analyzed with a full general circulation model. J. Geophys. Res. (Planets) 115(E14), E06006.Google Scholar
Lebonnois, S., Burgalat, J., Rannou, P. & Charnay, B. (2012). Titan global climate model: a new 3-dimensional version of the IPSL Titan GCM. Icarus 218, 707722.Google Scholar
Leconte, J., Forget, F., Charnay, B., Wordsworth, R., Selsis, F. & Millour, E. (2013). 3D climate modeling of close-in land planets: circulation patterns, climate moist bistability and habitability. Astron. Astrophys., in press. ArXiv e-prints arXiv:1303.7079.CrossRefGoogle Scholar
Léger, A. et al. (2009). Transiting exoplanets from the CoRoT space mission. VIII. CoRoT-7b: the first super-Earth with measured radius. Astron. Astrophys. 506, 287302.CrossRefGoogle Scholar
Lenardic, A. & Crowley, J.W. (2012). On the notion of well-defined tectonic regimes for terrestrial planets in this solar system and others. Astrophys. J. 755, 132.Google Scholar
Lichtenegger, H.I.M., Lammer, H., Griemeier, J.-M., Kulikov, Y.N., von Paris, P., Hausleitner, W., Krauss, S. & Rauer, H. (2010). Aeronomical evidence for higher CO2 levels during Earth Hadean epoch. Icarus 210, 17.Google Scholar
Lissauer, J.J. et al. (2011). A closely packed system of low-mass, low-density planets transiting Kepler-11. Nature 470, 5358.CrossRefGoogle ScholarPubMed
Longdoz, B. & Francois, L.M. (1997). The faint young sun paradox: influence of the continental configuration and of the seasonal cycle on the climatic stability. Global Planet. Change 14, 97112.Google Scholar
Mayor, M. & Queloz, D. (2012). From 51 peg to Earth-type planets. New Astron. Rev. 56, 1924.CrossRefGoogle Scholar
Mayor, M. et al. (2009). The HARPS search for southern extra-solar planets. XVIII. An Earth-mass planet in the GJ 581 planetary system. Astron. Astrophys. 507, 487–294.CrossRefGoogle Scholar
McKay, C.P., Porco, C.C., Altheide, T., Davis, W.L. & Kral, T.A. (2008). The possible origin and persistence of life on enceladus and detection of biomarkers in the plume. Astrobiology 8, 909919.Google Scholar
Nimmo, F. & McKenzie, D. (1998). Volcanism and tectonics on Venus. Annu. Rev. Earth Planet. Sci. 26, 2353.Google Scholar
O'Neill, C. & Lenardic, A. (2007). Geological consequences of super-sized Earths. Geophys. Res. Lett. 34, 19204.Google Scholar
Pepe, F., Lovis, C., Ségransan, D., Benz, W., Bouchy, F., Dumusque, X., Mayor, M., Queloz, D., Santos, N.C. & Udry, S. (2011). The HARPS search for Earth-like planets in the habitable zone. I. Very low-mass planets around HD 20794, HD 85512, and HD 192310. Astron. Astrophys. 534, A58.Google Scholar
Pierrehumbert, R. & Gaidos, E. (2011). Hydrogen greenhouse planets beyond the habitable zone. Astrophys. J. Lett. 734, L13.CrossRefGoogle Scholar
Rosing, M.T. (2005). Thermodynamics of life on the planetary scale. Int. J. Astrobiol. 4, 911.CrossRefGoogle Scholar
Rothschild, L.J. & Mancinelli, R.L. (2001). Life in extreme environments. Nature 409, 10921101.Google Scholar
Sagan, C. (1996). Circumstellar habitable zones: an introduction. In Circumstellar Habitable Zones, ed. Doyle, L.R.Travis House, Menlo Park, CA, pp. 314.Google Scholar
Sagan, C. & Chyba, C. (1997). The early faint young Sun paradox: organic shielding of ultraviolet-labile greenhouse gases. Science 276, 12171221.CrossRefGoogle Scholar
Santerne, A., Diaz, R.F., Moutou, C., Bouchy, F., Hébrard, G., Almenara, J.-M., Bonomo, A.S., Deleuil, M. & Santos, N.C. (2012). SOPHIE velocimetry of Kepler transit candidates. VII. A false-positive rate of 35% for Kepler close-in giant candidates. Astron. Astrophys. 545, A76.Google Scholar
Sellers, W. (1969). A climate model based on the energy balance of the Earth-atmosphere system. J. Appl. Met. 8, 392400.Google Scholar
Selsis, F., Kasting, J.F., Levrard, B., Paillet, J., Ribas, I. & Delfosse, X. (2007). Habitable planets around the star Gliese 581? Astron. Astrophys. 476, 13731387.Google Scholar
Spiegel, D.S., Menou, K. & Scharf, C.A. (2008). Habitable climates. Astrophys. J. 681, 16091623.CrossRefGoogle Scholar
Stamenkovic, V., Noack, L., Breuer, D. & Spohn, T. (2012). The influence of pressure-dependent viscosity on the thermal evolution of super-earths. Astrophys. J. 748, 41.Google Scholar
Stein, C., Finnenkötter, A., Lowman, J.P. & Hansen, U. (2011). The pressure-weakening effect in super-Earths: consequences of a decrease in lower mantle viscosity on surface dynamics. Geophys. Res. Lett. 38, L21201, doi:10.1029/2011GL049341.Google Scholar
Tarter, J.C. et al. (2007). A reappraisal of the habitability of planets around M dwarf stars. Astrobiology 7, 3065.Google Scholar
Tian, F. (2011). The nitrogen constraint on habitability of planets around low mass M-stars. In EPSC-DPS Joint Meeting 2011, p. 380.Google Scholar
Tinetti, G. et al. (2012). EChO. Experimental Astronomy, p. 35.CrossRefGoogle Scholar
Tuomi, M., Anglada-Escudé, G., Gerlach, E., Jones, H.R.A., Reiners, A., Rivera, E.J., Vogt, S.S. & Butler, R.P. (2013). Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307. Astron. Astrophys. 549, A48.Google Scholar
Udry, S. et al. (2007). The HARPS search for southern extra-solar planets. XI. Super-Earths (5 and 8 M+) in a 3-planet system. Astron. Astrophys. 469, L43.Google Scholar
Valencia, D. & O'Connell, R.-J. (2009). Convection scaling and subduction on Earth and super-Earths. Earth Planet. Sci. Lett. 286, 492502.CrossRefGoogle Scholar
Valencia, D., O'Connell, R.J. & Sasselov, D.D. (2007). Inevitability of plate tectonics on super-Earths. Astrophys. J. 670, L45L48.CrossRefGoogle Scholar
Van Heck, H.J. & Tackley, P.J. (2011). Plate tectonics on super-Earths: equally or more likely than on Earth. Earth Planet. Sci. Lett. 310, 252261.Google Scholar
Von Paris, P., Gebauer, S., Godolt, M., Grenfell, J.L., Hedelt, P., Kitzmann, D., Patzer, A.B.C., Rauer, H. & Stracke, B. (2010). The extrasolar planet Gliese 581d: a potentially habitable planet? Astron. Astrophys. 522, A23.Google Scholar
Von Paris, P., Gebauer, S., Godolt, M., Rauer, H. & Stracke, B. (2011). Atmospheric studies of habitability in the Gliese 581 system. Astron. Astrophys. 532, A58.Google Scholar
Walker, J.C.G., Hays, P.B. & Kasting, J.F. (1981). A negative feedback mechanism for the long term stabilization of the Earth's surface temperature. J. Geophys. Res. 86, 97769782.CrossRefGoogle Scholar
Ward, P.D. & Brownlee, D. (2000). Rare Earth. Why Complex Life is Uncommon in the Universe. Copernicus Books, New York.CrossRefGoogle Scholar
Williams, D.M. & Kasting, J.F. (1997). Habitable planets with high obliquities. Icarus 129, 254267.CrossRefGoogle ScholarPubMed
Wordsworth, R. (2012). Transient conditions for biogenesis on low-mass exoplanets with escaping hydrogen atmospheres. Icarus 219, 267273.Google Scholar
Wordsworth, R., Forget, F. & Eymet, V. (2010a). Infrared collision-induced and far-line absorption in dense CO2 atmospheres. Icarus 210, 992997.Google Scholar
Wordsworth, R.D., Forget, F., Selsis, F., Madeleine, J.-B., Millour, E. & Eymet, V. (2010b). Is Gliese 581d habitable? Some constraints from radiative-convective climate modeling. Astron. Astrophys. 522, A22.Google Scholar
Wordsworth, R.D., Forget, F., Selsis, F., Millour, E., Charnay, B. & Madeleine, J.-B. (2011). Gliese 581d is the first discovered terrestrial-mass exoplanet in the habitable zone. Astrophys. J. Lett. 733, L48.Google Scholar