Could photosynthesis function on Proxima Centauri b?

摘要

Could oxygenic and/or anoxygenic photosynthesis exist on planet Proxima Centauri b? Proxima Centauri (spectral type - M5.5 V, 3050 K) is a red dwarf, whereas the Sun is type G2 V (5780 K). The light regimes on Earth and Proxima Centauri b are compared with estimates of the planet's suitability for Chlorophyll a (Chl a) and Chl d-based oxygenic photosynthesis and for bacteriochlorophyll (BChl)-based anoxygenic photosynthesis. Proxima Centauri b has low irradiance in the oxygenic photosynthesis range (400-749 nm: 64-132 mu mol quanta m(-2) s(-1)). Much larger amounts of light would be available for BChl-based anoxygenic photosynthesis (350-1100 nm: 724-1538 mu mol quanta m(-2) s(-1)). We estimated primary production under these light regimes. We used the oxygenic algae Synechocystis PCC6803, Prochlorothrix hollandica, Acaryochloris marina, Chlorella vulgaris, Rhodomonas sp. and Phaeodactylum tricornutum and the anoxygenic photosynthetic bacteria Rhodopseudomonas palustris (BChl a), Afifella marina (BChl a), Thermochromatium tepidum (BChl a), Chlorobaculum tepidum (BChl a + c) and Blastochloris viridis (BChl b) as representative photosynthetic organisms. Proxima Centauri b has only approximate to 3% of the PAR (400-700 nm) of Earth irradiance, but we found that potential gross photosynthesis (P-g) on Proxima Centauri b could be surprisingly high (oxygenic photosynthesis: earth approximate to 0.8 gC m(-2) h(-1); Proxima Centauri b approximate to 0.14 gC m(-2) h(-1)). The proportion of PAR irradiance useable by oxygenic photosynthetic organisms (the sum of Blue + Red irradiance) is similar for the Earth and Proxima Centauri b. The oxygenic photic zone would be only approximate to 10 m deep in water compared with approximate to 200 m on Earth. The P-g of an anoxic Earth (gC m(-2) h(-1)) is approximate to 0.34-0.59 (land) and could be as high as approximate to 0.29-0.44 on Proxima Centauri b. 1 m of water does not affect oxygenic or anoxygenic photosynthesis on Earth, but