Purple Photosynthesis: Unraveling the Past of Early Earth with New Discoveries in Bioluminescence and Astronomy

Purple archaea may have been the dominant life form on early Earth, as they used a molecule called retinal to photosynthesize before the planet was filled with oxygen. A study from 2018 explored the potential life forms that could have existed on Earth in its early days. Shiladitya DesSarma, a molecular biologist at the University of Maryland, led this research.

Recent studies have added spectral data on 20 species of purple bacteria, collected from various environments such as marshes and deep-sea hydrothermal vents. By measuring the wavelengths of light these bacteria reflect and modeling how these patterns may appear on a distant planet, scientists have created a collection of light signatures. This information is now part of an ongoing database that is publicly available for other researchers to use in their own projects.

Astronomers search for signs of life on other planets using biosignatures such as the color of a planet’s surface. Reflected light spectroscopy is often used for this purpose, but current telescopes are limited in their capabilities. For example, the James Webb Space Telescope can only detect biosignatures in an exoplanet’s atmosphere and cannot measure reflected light from the planet’s surface. Edward Schwieterman, an astronomer at the University of California Riverside, emphasizes this limitation.