Aquatic Biospheres On Temperate Planets Around Sun-like Stars And M-dwarfs

In both panels, the photon flux in units of the compensation flux (FC ) is shown for an Earth-analog orbiting a solar twin (Planet G) as a function of the depth; the compensation flux specifies the photon flux at which net growth of the organism is not feasible. The various curves correspond to different choices of the global ocean temperature, and the intersection points of the various curves with the dashed horizontal line yield the compensation depths. In the left panel, the optimistic case with minimal attenuation and maximum incident stellar flux is illustrated. In the right panel, the realistic case that duly accounts for both these is depicted.

Aquatic biospheres reliant on oxygenic photosynthesis are expected to play an important role on Earth-like planets with large-scale oceans insofar as carbon fixation (i.e., biosynthesis of organic compounds) is concerned.

We investigate the properties of aquatic biospheres comprising Earth-like biota for habitable rocky planets orbiting Sun-like stars and late-type M-dwarfs such as TRAPPIST-1. In particular, we estimate how these characteristics evolve with the ambient ocean temperature (TW), which is a key environmental variable.

We show that many salient properties, such as the depth of the photosynthesis zone and the net primary productivity (i.e., the effective rate of carbon fixation), are sensitive to TW, and eventually decline substantially as the ocean temperature is increased. We conclude by discussing the implications of our analysis for the past and future Earth, and exoplanets orbiting M-dwarfs.

Manasvi Lingam, Abraham Loeb
Comments: 15 pages; 4 figures; 1 table
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Populations and Evolution (q-bio.PE)
Cite as: arXiv:2005.14387 [astro-ph.EP] (or arXiv:2005.14387v1 [astro-ph.EP] for this version)
Submission history
From: Manasvi Lingam
[v1] Fri, 29 May 2020 05:04:13 UTC (453 KB)

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