Early evolution of purple retinal pigments on Earth and implications for exoplanet biosignatures

  title={Early evolution of purple retinal pigments on Earth and implications for exoplanet biosignatures},
  author={Shiladitya DasSarma and Edward W. Schwieterman},
  journal={International Journal of Astrobiology},
We propose that retinal-based phototrophy arose early in the evolution of life on Earth, profoundly impacting the development of photosynthesis and creating implications for the search for life beyond our planet. While the early evolutionary history of phototrophy is largely in the realm of the unknown, the onset of oxygenic photosynthesis in primitive cyanobacteria significantly altered the Earth's atmosphere by contributing to the rise of oxygen ~2.3 billion years ago. However, photosynthetic… 

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