Recent research indicates that astronomers might need to examine the purple areas in the universe to detect signs of life on distant planets.
This study has identified light signals coming from worlds without sunlight and oxygen, similar to many exoplanets discovered to date. On Earth, the dominant color associated with life is green, due to plants and bacteria that transform sunlight into energy with the help of green chlorophyll.
However, scientists speculate that organisms on planets orbiting smaller, dimmer stars could survive by metabolizing other forms of infrared light. Such bacteria, powered by infrared light, already exist in various environments on Earth, such as deep-sea hydrothermal vents and murky marshes, where sunlight does not penetrate.
The color purple might be as significant as green in the quest for signs of alien life
A study published in the journal Monthly Notices of the Royal Astronomical Society, led by astrobiologist Ligia Fonseca Coelho from Cornell University, involved growing various bacteria and measuring the wavelengths of light they reflected. This data was then used to simulate the light signals that might be observed in other worlds.
The researchers suggest that telescopes like the Extremely Large Telescope, currently under construction in Chile, and the planned Habitable Worlds Observatory, will be capable of detecting these unique light spectra. Lisa Kaltenegger, the director of the Carl Sagan Institute and a Cornell University astronomer who co-authored the study said, “We need to create a database for signs of life to make sure our telescopes don’t miss life if it happens not to look exactly like what we encounter around us every day.”
According to scientists, purple bacteria, classified in the phylum Pseudomonadota, can thrive in environments with low oxygen levels. Ligia Fonseca Coelho and her colleagues grew twenty species of purple non-sulfur-producing bacteria and twenty species of purple sulfur-producing bacteria. These bacteria were collected from various sources, including existing lab cultures, a pond on Cornell’s campus in upstate New York, and waters near Cape Cod, Massachusetts.
“Our models show that depending on the surface coverage of the biota and the cloud coverage, a wide variety of terrestrial planets could show signs of purple bacteria surface biopigments,” stated the researchers, in their paper.
“While it is unknown whether life — or purple bacteria — can evolve on other worlds, purple might just be the new green in the search for surface life,” they added.