Photosynthesis offers a convenient means of sustaining biospheres. We quantify the constraints for photosynthesis to be functional on the permanent nightside of tidally locked rocky exoplanets via reflected light from their exomoons. We show that the exomoons must be at least half the size of Earth's moon in order for conventional oxygenic photosynthesis to operate. This scenario of photosynthesis is unlikely for exoplanets around late-type M-dwarfs due to the low likelihood of large exomoons and their orbital instability over long timescales. Subsequently, we investigate the prospects for photosynthesis on habitable exomoons via reflected light from the giant planets that they orbit. Our analysis indicates that such photosynthetic biospheres are potentially sustainable on these moons except those around late-type M-dwarfs. We conclude our analysis by delineating certain physiological and biochemical features of photosynthesis and other carbon fixation pathways, and the likelihood of their evolution on habitable planets and moons.

中文翻译：

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来自反射光的系外行星和系外卫星的光合作用

光合作用提供了维持生物圈的便捷方式。我们通过来自它们的外卫星的反射光来量化光合作用在潮汐锁定的岩石系外行星的永久夜间起作用的限制。我们表明，外卫星必须至少是地球月球大小的一半，才能进行常规的含氧光合作用。由于大型系外卫星的可能性很低，而且它们的轨道在很长一段时间内不稳定，这种光合作用的情况不太可能发生在晚期 M 型矮星周围的系外行星上。随后，我们通过它们环绕的巨行星的反射光研究了宜居系外卫星上光合作用的前景。我们的分析表明，除了晚期 M 型矮星周围的那些卫星之外，这些卫星上的这种光合生物圈可能是可持续的。