Edinburgh Research Explorer

What makes a planet habitable?

Research output: Contribution to journalLiterature review

  • H. Lammer
  • J. H. Bredehoeft
  • A. Coustenis
  • M. L. Khodachenko
  • L. Kaltenegger
  • O. Grasset
  • D. Prieur
  • F. Raulin
  • P. Ehrenfreund
  • M. Yamauchi
  • J. -E. Wahlund
  • J. -M. Griessmeier
  • G. Stangl
  • C. S. Cockell
  • Yu. N. Kulikov
  • J. L. Grenfell
  • H. Rauer
  • Charles Cockell

Related Edinburgh Organisations

Original languageEnglish
Pages (from-to)181-249
Number of pages69
JournalAstronomy and astrophysics review
Volume17
Issue number2
DOIs
Publication statusPublished - Jun 2009

Abstract

This work reviews factors which are important for the evolution of habitable Earth-like planets such as the effects of the host star dependent radiation and particle fluxes on the evolution of atmospheres and initial water inventories. We discuss the geodynamical and geophysical environments which are necessary for planets where plate tectonics remain active over geological time scales and for planets which evolve to one-plate planets. The discoveries of methane-ethane surface lakes on Saturn's large moon Titan, subsurface water oceans or reservoirs inside the moons of Solar System gas giants such as Europa, Ganymede, Titan and Enceladus and more than 335 exoplanets, indicate that the classical definition of the habitable zone concept neglects more exotic habitats and may fail to be adequate for stars which are different from our Sun. A classification of four habitat types is proposed. Class I habitats represent bodies on which stellar and geophysical conditions allow Earth-analog planets to evolve so that complex multi-cellular life forms may originate. Class II habitats includes bodies on which life may evolve but due to stellar and geophysical conditions that are different from the class I habitats, the planets rather evolve toward Venus- or Mars-type worlds where complex life-forms may not develop. Class III habitats are planetary bodies where subsurface water oceans exist which interact directly with a silicate-rich core, while class IV habitats have liquid water layers between two ice layers, or liquids above ice. Furthermore, we discuss from the present viewpoint how life may have originated on early Earth, the possibilities that life may evolve on such Earth-like bodies and how future space missions may discover manifestations of extraterrestrial life.

    Research areas

  • Habitability, Origin of life, Terrestrial planets, Subsurface oceans, Atmosphere evolution, Earth-like exoplanets, Space weather, Astrobiology, EARTH-LIKE PLANETS, MAIN-SEQUENCE STARS, SOLAR-TYPE STARS, EJECTION CME ACTIVITY, MASS-LOSS RATES, MAGNETIC-FIELD, ATMOSPHERIC EVOLUTION, TERRESTRIAL PLANETS, INTERSTELLAR-MEDIUM, ISHTAR TERRA

ID: 1498255