ExoPhot: Developing a new metric for measuring the fitness of photosystem activity in an exoplanetary environment.
Authors: Marcos-Arenal Pablo , Cerdán Luis , Burillo-Villalobos Mercedes , Fonseca-Bonilla Nuria , García de la Concepción Juan , Gómez Felipe , Caballero José Antonio 
Published: September 2022

&lt;p&gt;Photosynthesis in our planet sustains all life by converting the radiation from our Sun to chemical energy. This metabolic route only requires water and carbon dioxide (Hall &amp; Rao 1999; Blankenship 2021) to be present in any exoplanet retaining an atmosphere (Hu et al. 2012; Trifonov et al. 2021) and transform the light from its host star to a biological source of energy.&lt;/p&gt;
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&lt;p&gt;We came up with an algorithm that combines the characteristics of an exoplanet and its atmosphere, its host star and some photosynthetic systems for assessing the feasibility of photosynthetic activity in an exoplanetary system.&lt;/p&gt;
&lt;p&gt;This algorithm provides a new metric, the total absorption rate, &amp;#947;t, for evaluating the likeliness of detecting biomarkers from the live organisms producing photosynthesis in that system. It can also be figured as an indicator of the evolutionary path of primeval pigments, and can help us understand the steps that led to the highly evolved chlorophylls and analogues existing on the Earth (Garc&amp;#237;a de la Concepci&amp;#243;n et al., subm.).&lt;/p&gt;
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&lt;p&gt;There are some previous metrics related to this topic like the photosynthetic photon flux density, or the total stellar irradiance, but do not provide with absolute quantitative results.&lt;/p&gt;
&lt;p&gt;We compare these metrics that relate the spectral type of the host star, the composition and properties of the atmosphere of the planet, and the different varieties of photopigments that they might host (Kiang et al. 2007; Komatsu et al. 2015; Gale &amp; Wandel 2017; Ritchie et al. 2018; Mullan &amp; Bais 2018; Lehmer et al. 2018, 2021; Lingam &amp; Loeb 2019, 2020; Covone et al. 2021; Lingam et al. 2021) to the total absorption rate.&lt;/p&gt;
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&lt;p&gt;References:&lt;/p&gt;
&lt;p&gt;Blankenship, R. E. 2021, Molecular mechanisms of photosynthesis (John Wiley &amp; Sons)&lt;/p&gt;
&lt;p&gt;Covone, G., Ienco, R. M., Cacciapuoti, L., &amp; Inno, L. 2021, Monthly Notices of the Royal Astronomical Society, 505, 3329&lt;/p&gt;
&lt;p&gt;Gale, J. &amp; Wandel, A. 2017, International Journal of Astrobiology, 16, 1&lt;/p&gt;
&lt;p&gt;Hall, D. O. &amp; Rao, K. 1999, Photosynthesis (Cambridge University Press)&lt;/p&gt;
&lt;p&gt;Hu, R., Seager, S., &amp; Bains, W. 2012, Astrophysical Journal, 761 [arXiv:1210.6885]&lt;/p&gt;
&lt;p&gt;Kiang, N. Y., Segura, A., Tinetti, G., et al. 2007, Astrobiology, 7, 252, pMID:17407410&lt;/p&gt;
&lt;p&gt;Komatsu, Y., Umemura, M., Shoji, M., et al. 2015, International Journal of Astrobiology, 14, 505&amp;#8211;510&lt;/p&gt;
&lt;p&gt;Lehmer, O. R., Catling, D. C., Parenteau, M. N., &amp; Hoehler, T. M. 2018, The Astrophysical Journal, 859, 171&amp;#160;&lt;/p&gt;
&lt;p&gt;Lehmer, O. R., Catling, D. C., Parenteau, M. N., Kiang, N. Y., &amp; Hoehler, T. M. 2021, Frontiers in Astronomy and Space Sciences, 8&lt;/p&gt;
&lt;p&gt;Lingam, M., Balbi, A., &amp; Mahajan, S. M. 2021, The Astrophysical Journal Letters, 921, L41&lt;/p&gt;
&lt;p&gt;Lingam, M. &amp; Loeb, A. 2019, Monthly Notices of the Royal Astronomical Society, 485, 5924&lt;/p&gt;
&lt;p&gt;Lingam, M. &amp; Loeb, A. 2020, The Astrophysical Journal Letters, 889, l15&lt;/p&gt;
&lt;p&gt;Mullan, D. J. &amp; Bais, H. P. 2018, The Astrophysical Journal, 865, 101&lt;/p&gt;
&lt;p&gt;Ritchie, R. J., Larkum, A. W., &amp; Ribas, I. 2018, International Journal of Astrobiology, 17, 147&amp;#8211;176&lt;/p&gt;
&lt;p&gt;Trifonov, T., Caballero, J., Morales, J., et al. 2021, Science, 371, 1038&lt;/p&gt;