The Peak Absorbance Wavelength of Photosynthetic Pigments Around Other Stars From Spectral Optimization
In the search for life on other planets, the presence of photosynthetic surface vegetation may be detectable from the colors of light it reflects. On the modern Earth, this spectral reflectance is characterized by a steep increase in reflectance between the red and near‐infrared wavelengths, a signa...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Frontiers Media S.A.
2021-07-01
|
| Series: | Frontiers in Astronomy and Space Sciences |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/articles/10.3389/fspas.2021.689441/full |
| _version_ | 1818846793859858432 |
|---|---|
| author | Owen R. Lehmer Owen R. Lehmer David C. Catling Mary N. Parenteau Nancy Y. Kiang Tori M. Hoehler |
| author_facet | Owen R. Lehmer Owen R. Lehmer David C. Catling Mary N. Parenteau Nancy Y. Kiang Tori M. Hoehler |
| author_sort | Owen R. Lehmer |
| collection | DOAJ |
| description | In the search for life on other planets, the presence of photosynthetic surface vegetation may be detectable from the colors of light it reflects. On the modern Earth, this spectral reflectance is characterized by a steep increase in reflectance between the red and near‐infrared wavelengths, a signature known as the “red edge”. This edge-like signature occurs at wavelengths of peak photon absorbance, which are the result of adaptations of the phototroph to their spectral environment. 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 energy losses due to thermal emission and building cellular 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 absorbance spectra for photosynthetic surface organisms 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 the weak spectral signal of red edge analogs. |
| first_indexed | 2024-12-19T05:51:12Z |
| format | Article |
| id | doaj.art-1d77a00494464bae89518404267d7921 |
| institution | Directory Open Access Journal |
| issn | 2296-987X |
| language | English |
| last_indexed | 2024-12-19T05:51:12Z |
| publishDate | 2021-07-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Astronomy and Space Sciences |
| spelling | doaj.art-1d77a00494464bae89518404267d79212022-12-21T20:33:36ZengFrontiers Media S.A.Frontiers in Astronomy and Space Sciences2296-987X2021-07-01810.3389/fspas.2021.689441689441The Peak Absorbance Wavelength of Photosynthetic Pigments Around Other Stars From Spectral OptimizationOwen R. Lehmer0Owen R. Lehmer1David C. Catling2Mary N. Parenteau3Nancy Y. Kiang4Tori M. Hoehler5Exobiology Branch, Ames Research Center, National Aeronautics and Space Administration (NASA), Moffet Field, CA, United StatesUniversity of Washington, Seattle, WA, United StatesUniversity of Washington, Seattle, WA, United StatesExobiology Branch, Ames Research Center, National Aeronautics and Space Administration (NASA), Moffet Field, CA, United StatesGoddard Institute for Space Studies (NASA), New York, NY, United StatesExobiology Branch, Ames Research Center, National Aeronautics and Space Administration (NASA), Moffet Field, CA, United StatesIn the search for life on other planets, the presence of photosynthetic surface vegetation may be detectable from the colors of light it reflects. On the modern Earth, this spectral reflectance is characterized by a steep increase in reflectance between the red and near‐infrared wavelengths, a signature known as the “red edge”. This edge-like signature occurs at wavelengths of peak photon absorbance, which are the result of adaptations of the phototroph to their spectral environment. 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 energy losses due to thermal emission and building cellular 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 absorbance spectra for photosynthetic surface organisms 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 the weak spectral signal of red edge analogs.https://www.frontiersin.org/articles/10.3389/fspas.2021.689441/fullbiosignaturephotosynthesispigmentred edgeexoplanetreflectance |
| spellingShingle | Owen R. Lehmer Owen R. Lehmer David C. Catling Mary N. Parenteau Nancy Y. Kiang Tori M. Hoehler The Peak Absorbance Wavelength of Photosynthetic Pigments Around Other Stars From Spectral Optimization Frontiers in Astronomy and Space Sciences biosignature photosynthesis pigment red edge exoplanet reflectance |
| title | The Peak Absorbance Wavelength of Photosynthetic Pigments Around Other Stars From Spectral Optimization |
| title_full | The Peak Absorbance Wavelength of Photosynthetic Pigments Around Other Stars From Spectral Optimization |
| title_fullStr | The Peak Absorbance Wavelength of Photosynthetic Pigments Around Other Stars From Spectral Optimization |
| title_full_unstemmed | The Peak Absorbance Wavelength of Photosynthetic Pigments Around Other Stars From Spectral Optimization |
| title_short | The Peak Absorbance Wavelength of Photosynthetic Pigments Around Other Stars From Spectral Optimization |
| title_sort | peak absorbance wavelength of photosynthetic pigments around other stars from spectral optimization |
| topic | biosignature photosynthesis pigment red edge exoplanet reflectance |
| url | https://www.frontiersin.org/articles/10.3389/fspas.2021.689441/full |
| work_keys_str_mv | AT owenrlehmer thepeakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT owenrlehmer thepeakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT davidccatling thepeakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT marynparenteau thepeakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT nancyykiang thepeakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT torimhoehler thepeakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT owenrlehmer peakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT owenrlehmer peakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT davidccatling peakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT marynparenteau peakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT nancyykiang peakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization AT torimhoehler peakabsorbancewavelengthofphotosyntheticpigmentsaroundotherstarsfromspectraloptimization |