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Researchers are expanding the criteria for life on other planets beyond the familiar green of Earthly vegetation. Scientists at Cornell University have suggested that purple, not green, might be the predominant color of life on other worlds, based on a study of bacteria that absorb infrared light for photosynthesis.
These purple bacteria, which exhibit a range of hues including yellow, ora by Clarence Oxford
Los Angeles CA (SPX) Apr 17, 2024
Researchers are expanding the criteria for life on other planets beyond the familiar green of Earthly vegetation. Scientists at Cornell University have suggested that purple, not green, might be the predominant color of life on other worlds, based on a study of bacteria that absorb infrared light for photosynthesis.
These purple bacteria, which exhibit a range of hues including yellow, orange, and red, could dominate planets orbiting cooler red dwarf stars, the most common type in the Milky Way. The findings were detailed by Ligia Fonseca Coelho, a postdoctoral associate at the Carl Sagan Institute, in her study titled "Purple is the New Green: Biopigments and Spectra of Earth-like Purple Worlds."
"Purple bacteria can thrive under a wide range of conditions, making it one of the primary contenders for life that could dominate a variety of worlds," Coelho explained.
The study emphasizes the importance of building a comprehensive database of signs of life to guide the development of telescopes capable of detecting these organisms from afar. The varied biopigments of purple bacteria, akin to the compounds that color tomatoes and carrots, would produce distinct light fingerprints, detectable by advanced telescopes.
"These organisms already prosper in niche environments here on Earth," Coelho added. "In worlds orbiting a red sun, they could find optimal conditions for photosynthesis."
The researchers also simulated environments where purple bacteria thrived on different types of Earth-like planets. This included models of frozen worlds, ocean planets, and more, all showing strong, colorful biosignatures.
"If we identify a 'pale purple dot' in a distant solar system, it will prompt close scrutiny to determine the source of its color, which could also be from vivid minerals," said Lisa Kaltenegger, director of the Carl Sagan Institute and co-author of the study.
Kaltenegger, who is also penning the book "Alien Earths: The New Science of Planet Hunting in the Cosmos," notes that discovering even simple life forms on another planet would imply that life is likely common across the universe. This would profoundly shift our understanding of our place in the cosmos.
"We are just opening our eyes to these fascinating worlds around us," she concluded. "Purple may indeed be the new green in our search for life beyond Earth."
Research Report:Purple is the New Green: Biopigments and Spectra of Earth-like Purple Worlds
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