Purple Earth: Rethinking Early Photosynthesis and the Search for Extraterrestrial Life
2025-07-27
The 'Purple Earth Hypothesis' proposes a radical reimagining of early Earth's biosphere. Scientists suggest that, between 3.5 and 2.4 billion years ago, life may have used retinal, a simpler molecule than chlorophyll, for photosynthesis, resulting in a purplish Earth. This retinal-based photosynthesis, simpler than chlorophyll-based systems, is seen in some modern extremophiles like halobacteria. This hypothesis not only challenges our understanding of early Earth but also expands the search for extraterrestrial life beyond the traditional focus on green planets.
Tech
Early Earth