The Possibility of Alien Life Being Purple

Recent studies have suggested that early Earth may have appeared purple due to the prevalence of purple microorganisms. These microorganisms, including purple archaea, use a molecule called retinal for photosynthesis and could have been dominant on Earth before the presence of oxygen. This expands the potential lifeforms that could have existed on our planet according to Shiladitya DesSarma, a molecular biologist at the University of Maryland and lead author of a 2018 study.

In a new paper, scientists have added spectral data on 20 species of purple bacteria found in various environments such as marshes and deep-sea hydrothermal vents. The researchers analyzed the wavelengths of light reflected by these bacteria and created models to predict how these patterns would appear on a distant planet. The resulting collection of light signatures is being added to a public database for use by other researchers in their projects.

Astronomers search for life on other planets using biosignatures, which can include the color of a planet’s surface. Reflected light spectroscopy is a technique used to observe these biosignatures, but current telescopes like the James Webb Space Telescope are limited in their abilities. While these telescopes can detect gases in an exoplanet’s atmosphere, they cannot measure the reflected light from the planet’s surface. Edward Schwieterman, an astronomer at the University of California Riverside, notes that advancements in observing technologies are necessary to analyze the surface features of distant planets for potential signs of life.