Oxygenic photosynthesis generates both atmospheric and surface biosignatures, making it a primary target in the search for life beyond Earth. The release of atmospheric oxygen and the distinctive reflectance spectra produced by photosynthetic pigments represent two potentially detectable indicators of biological activity on exoplanets. Because many potentially habitable planets have been found orbiting the habitable zones of M-dwarf stars, a central question in astrobiology is whether oxygenic photosynthesis could operate under the spectral conditions of these stars and generate detectable biosignatures.

Most known oxygenic phototrophs rely on visible light (VIS, 400–700 nm) to drive photosynthesis. However, planets orbiting M-dwarfs receive radiation that is relatively depleted in visible wavelengths and enriched in far-red and infrared light (FR, 700–750 nm; IR, 750–1000 nm), spectral regions that generally do not support conventional oxygenic photosynthesis. Nevertheless, several terrestrial environments provide natural analogues of these conditions. Far-red–enriched ecological niches on Earth host diverse oxygenic phototrophs capable of functioning under these light conditions thanks to a suite of unique physiological and structural features.

To investigate the astrobiological implications of these adaptations, we developed a laboratory platform that simulates key exoplanetary conditions, including an anoxic atmosphere and tailored irradiance spectra. The system also allows real-time monitoring of organism growth, oxygen evolution, and reflectance spectra.
By combining laboratory simulations with the study of photosynthetic diversity on Earth, our multidisciplinary research team in Padova, Italy, is exploring the plausibility of oxygenic photosynthesis on M-dwarf planets and the biosignatures it could produce.