Publication Abstracts

Schwieterman et al. 2019

Schwieterman, E.W., C.T. Reinhard, S.L. Olson, C.E. Harman, and T.W. Lyons, 2019: A limited habitable zone for complex life. Astrophys. J., 878, no. 1, 19, doi:10.3847/1538-4357/ab1d52.

The habitable zone (HZ) is defined as the range of distances from a host star within which liquid water, a key requirement for life, may exist at a planet's surface. Substantially more CO2 than present in Earth's modern atmosphere is required to maintain clement temperatures for most of the HZ, with several bars required at the outer edge. However, most complex aerobic life on Earth is limited by CO2 concentrations of just fractions of a bar. At the same time, most exoplanets in the traditional HZ reside in proximity to M dwarfs, which are more numerous than Sun-like G dwarfs but are predicted to promote greater abundances of gases that can be toxic in the atmospheres of orbiting planets, such as carbon monoxide (CO). Here we show that the HZ for complex aerobic life is likely limited relative to that for microbial life. We use 1D radiative-convective climate and photochemical models to circumscribe a Habitable Zone for Complex Life (HZCL) based on known toxicity limits for a range of complex organisms as a proof of concept. We find that for CO2 tolerances of 0.01, 0.1, and 1 bar, the HZCL is only only 21%, 32%, and 50% as wide as the conventional HZ for a Sun-like star, and that CO concentrations may limit some complex life throughout the entire HZ of the coolest M dwarfs. These results cast new light on the likely distribution of complex life in the universe and have important practical ramifications for the search for exoplanet biosignatures and technosignatures.

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BibTeX Citation

  author={Schwieterman, E. W. and Reinhard, C. T. and Olson, S. L. and Harman, C. E. and Lyons, T. W.},
  title={A limited habitable zone for complex life},
  journal={Astrophys. J.},

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RIS Citation

ID  - sc01700t
AU  - Schwieterman, E. W.
AU  - Reinhard, C. T.
AU  - Olson, S. L.
AU  - Harman, C. E.
AU  - Lyons, T. W.
PY  - 2019
TI  - A limited habitable zone for complex life
JA  - Astrophys. J.
VL  - 878
IS  - 1
SP  - 19
DO  - 10.3847/1538-4357/ab1d52
ER  -

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