Journal article
A Two-Tiered Approach to Assessing the Habitability of Exoplanets
Astrobiology, Vol.11(10), pp.141-1052
12/01/2011
Handle:
https://hdl.handle.net/2376/113145
PMID: 22017274
Abstract
In the next few years, the number of catalogued exoplanets will be counted in the thousands. This will vastly expand the number of potentially habitable worlds and lead to a systematic assessment of their astrobiological potential. Here, we suggest a two-tiered classification scheme of exoplanet habitability. The first tier consists of an Earth Similarity Index (ESI), which allows worlds to be screened with regard to their similarity to Earth, the only known inhabited planet at this time. The ESI is based on data available or potentially available for most exoplanets such as mass, radius, and temperature. For the second tier of the classification scheme we propose a Planetary Habitability Index (PHI) based on the presence of a stable substrate, available energy, appropriate chemistry, and the potential for holding a liquid solvent. The PHI has been designed to minimize the biased search for life as we know it and to take into account life that might exist under more exotic conditions. As such, the PHI requires more detailed knowledge than is available for any exoplanet at this time. However, future missions such as the Terrestrial Planet Finder will collect this information and advance the PHI. Both indices are formulated in a way that enables their values to be updated as technology and our knowledge about habitable planets, moons, and life advances. Applying the proposed metrics to bodies within our Solar System for comparison reveals two planets in the Gliese 581 system, GJ 581 c and d, with an ESI comparable to that of Mars and a PHI between that of Europa and Enceladus. Key Words: Habitability—Exoplanets—Index—Earth similarity—Complexity—Life. Astrobiology 11, 1041–1052.
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Details
- Title
- A Two-Tiered Approach to Assessing the Habitability of Exoplanets
- Creators
- Dirk Schulze-Makuch - 4Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, GermanyAbel Méndez - 2Planetary Habitability Laboratory, University of Puerto Rico at Arecibo, Arecibo, Puerto Rico, USAAlberto G Fairén - 3SETI Institute and NASA Ames Research Center, Moffett Field, California, USAPhilip von Paris - 4Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, GermanyCarol Turse - 1School of Earth and Environmental Sciences, Washington State University, Pullman, Washington, USAGrayson Boyer - 5Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, USAAlfonso F Davila - 3SETI Institute and NASA Ames Research Center, Moffett Field, California, USAMarina Resendes de Sousa António - 1School of Earth and Environmental Sciences, Washington State University, Pullman, Washington, USADavid Catling - 6Department of Earth and Space Sciences/Astrobiology Program, University of Washington, Seattle, Washington, USALouis N Irwin - 7Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas, USA
- Publication Details
- Astrobiology, Vol.11(10), pp.141-1052
- Academic Unit
- UNKNOWN
- Publisher
- Mary Ann Liebert, Inc
- Identifiers
- 99900548164601842
- Language
- English
- Resource Type
- Journal article