Publication Abstracts

Kiang et al. 2007

Kiang, N.Y., A. Segura, G. Tinetti, Govindjee, R.E. Blankenship, M. Cohen, J. Siefert, D. Crisp, and V.S. Meadows, 2007: Spectral signatures of photosynthesis II: Coevolution with other stars and the atmosphere on extrasolar worlds. Astrobiology, 7, 252-274, doi:10.1089/ast.2006.0108.

As photosynthesis on Earth produces the primary signatures of life that can be detected astronomically at the global scale, a strong focus of the search for extrasolar life will be photosynthesis, particularly photosynthesis that has evolved with a different parent star. We take planetary atmospheric compositions simulated by Segura, et al. (2003, 2005) for Earth-like planets around modeled F2V, K2V, M1V and M5V stars, and around the active M4.5V star AD Leo, with scenarios using Earth's atmospheric composition as well as very low O2 content, in case anoxygenic photosynthesis dominates. With a line-by-line radiative transfer model we calculate the incident spectral photon flux densities at the surface of the planet and under water. We identify bands of available photosynthetically relevant radiation, and find that photosynthetic pigments on planets around F2V stars may peak in absorbance in the blue, K2V in the red-orange, and M stars in the NIR, in bands at 0.93-1.1 µm, 1.1-1.4 µm, 1.5-1.8 µm, and 1.8-2.5 µm. However, underwater organisms will be restricted to wavelengths shorter than 1.4 µm and more likely below 1.1 µm. M star planets without oxygenic photosynthesis will have photon fluxes above 1.6 µm curtailed by methane. Longer-wavelength, multiphotosystem series would reduce the quantum yield but could allow for oxygenic photosystems at longer wavelengths, restricted to below 1.1 µm as a cut-off for electronic transitions vs. only vibrational energy; however, there is no strict upper wavelength bound, since such energetics depend on molecular configuration. M star planets could be a half to a tenth as productive as Earth in the visible, but exceed Earth if useful photons extend to 1.1 µm for anoxygenic photosynthesis. Under water, organisms would still be able to survive UV flares from young M stars and acquire adequate light for growth.

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BibTeX Citation

@article{ki09000a,
  author={Kiang, N. Y. and Segura, A. and Tinetti, G. and Govindjee and Blankenship, R. E. and Cohen, M. and Siefert, J. and Crisp, D. and Meadows, V. S.},
  title={Spectral signatures of photosynthesis II: Coevolution with other stars and the atmosphere on extrasolar worlds},
  year={2007},
  journal={Astrobiology},
  volume={7},
  pages={252--274},
  doi={10.1089/ast.2006.0108},
}

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RIS Citation

TY  - JOUR
ID  - ki09000a
AU  - Kiang, N. Y.
AU  - Segura, A.
AU  - Tinetti, G.
AU  - Govindjee
AU  - Blankenship, R. E.
AU  - Cohen, M.
AU  - Siefert, J.
AU  - Crisp, D.
AU  - Meadows, V. S.
PY  - 2007
TI  - Spectral signatures of photosynthesis II: Coevolution with other stars and the atmosphere on extrasolar worlds
JA  - Astrobiology
VL  - 7
SP  - 252
EP  - 274
DO  - 10.1089/ast.2006.0108
ER  -

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