The peak absorbance wavelength of photosynthetic pigments around other stars from spectral optimization

Abstract

In the search for life on other planets, the presence of photosynthetic vegetation may be detectable from the colors of light it reflects. On the modern Earth, this spectral reflectance is characterized by an increase in reflectance between the red and near-infrared wavelengths, a "red edge". On planets orbiting different stellar types, red edge analogs may occur at other colors than red. Thus, knowing the wavelengths at which photosynthetic organisms preferentially absorb and reflect photons is necessary to detect red edge analogs on other planets. Using a numerical model that predicts the absorbance spectrum of extant photosynthetic pigments on Earth from Marosvölgyi and van Gorkom (2010), we calculate the absorbance spectrum for pigments on an Earth-like planet around F through late M type stars that are adapted for maximal energy production. In this model, cellular energy production is maximized when pigments are tuned to absorb at the wavelength that maximizes energy input from incident photons while minimizing thermal emission and costs to build the photosynthetic apparatus. We find that peak photon absorption for photosynthetic organisms around F type stars tends to be in the blue while for G, K, and early M type stars, red or just beyond is preferred. Around the coolest M type stars, these organisms may preferentially absorb in the near-infrared, possibly past one micron. These predictions are consistent with previous, qualitative estimates of pigment absorptance. Our predicted pigment absorbance spectra depend on both the stellar type and planetary atmospheric composition, especially atmospheric water vapor concentrations, which alter the availability of surface photons and thus the predicted pigment absorption. By constraining the absorbance spectra of alien, photosynthetic organisms, future observations may be better equipped to detect red edge analogs.

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Cited by in corpus (7)

• Earth as an Exoplanet. II. Earth's Time-variable Thermal Emission and Its Atmospheric Seasonality of Bioindicators
• Excitation Properties of Photopigments and Their Possible Dependence on the Host Star
• Purple is the new green: biopigments and spectra of Earth-like purple worlds
• Potential for life to exist and be detected on Earth-like planets orbiting white dwarfs
• Photosynthetic Fluorescence from Earth-Like Planets around Sun-Like and Cool Stars
• A novel metric for assessing climatological surface habitability
• Photosynthetic exergy I. Thermodynamic limits for habitable-zone planets