Purple has emerged as the preferred hue for extraterrestrial life, challenging the conventional green depiction often associated with alien planets. Research conducted by Cornell University suggests that our traditional color assumptions may need a significant revision.
On Earth, the verdant green color of plants stems from chlorophyll pigments that facilitate photosynthesis by absorbing light. However, chlorophyll primarily absorbs light at the red and blue ends of the spectrum, leading to the reflection of green light and the characteristic green appearance of leaves.
The intriguing possibility arises when considering alternative energy absorption mechanisms employed by major photosynthesizing life forms on distant planets. While Earth hosts bacteria capable of harnessing invisible infrared radiation for energy, many of these bacteria boast purple pigments that reflect blue and red light, resulting in a distinct purple hue.
The adaptability and resilience of purple-pigmented photosynthesizers on Earth prompt speculation about the potential prevalence of purple as the dominant color for extraterrestrial life forms. Ligia Fonseca Coelho, a postdoctoral associate at Cornell University’s Carl Sagan Institute and lead author of the study, highlights the versatility of purple bacteria across diverse environmental conditions, positioning them as strong candidates for thriving on various worlds.
The absence of competition from green plants, algae, and bacteria could offer purple bacteria an advantageous niche, especially under the radiance of a red sun conducive to photosynthesis. This unique color adaptation underscores the significance of considering alternative color signatures in the search for extraterrestrial life beyond familiar terrestrial norms.
Coelho emphasizes the necessity of expanding our understanding of potential life indicators to ensure that telescopic observations remain inclusive of diverse life forms that may deviate from terrestrial standards. By modeling Earth-like planets with varying conditions and cloud cover, Coelho and her team explored the survival capabilities of different purple bacteria strains and the distinct color imprints they might exhibit under varying planetary environments.
Lisa Kaltenegger, co-author of the study and director of the Carl Sagan Institute, envisions a paradigm shift where purple could indeed become the new green on numerous alien worlds. This research illuminates the remarkable possibilities presented by the colorful diversity of life forms across the cosmos, inviting us to broaden our perspective on the captivating realms awaiting discovery beyond our familiar horizons.