With more than 5,500 exoplanets detected, the search for life is entering a new era. Astrobiologists from Cornell University and the University of Minnesota have used life on Earth as a guide to look beyond the lush landscape and expand our ability to detect signs of surface life on other worlds. A new study characterizes the reflectance spectra of purple sulfur and non-sulfur bacteria from different environments.
Coelho to extend the baseline for finding life in the universe other. They measured the reflectance of purple bacteria growing in different anoxic and aerobic environments. Image credit: Sci.News.
From houseplants and gardens to fields and forests, green is the color most associated with life on Earth’s surface. On Earth, conditions were favorable for the evolution of organisms that carried out photosynthesis, using the green pigment chlorophyll a to produce oxygen.
But an Earth-like planet orbiting another star could look completely different, receiving little or no visible light or oxygen and instead relying on photosynthesis, like some environments on Earth. may be covered in bacteria that use invisible infrared light to promote
Many such bacteria on Earth contain purple pigments instead of green, and in a world where they are predominantly purple, they could produce unique “light fingerprints” that can be detected by next generation ground and space telescopes. will be generated.
Ligia Fonseca Coelho, Ph.D., a postdoctoral fellow at Cornell University’s Carl Sagan Institute, said, “Purple bacteria are able to thrive under a wide range of conditions, making them one of the leading candidates for life that has the potential to dominate many different worlds.” “We have become one,” he said.
“We are building a database of signs of life so that telescopes can detect life even if they don’t look exactly like what we encounter around us every day,” said Dr. Lisa Kaltenegger, director of the Carl Sagan Institute. We need to make sure we don’t miss out,” he added. at Cornell University.
For this study, the authors collected samples of more than 20 types of purple sulfur and non-sulfur bacteria that can be found in a variety of environments, from shallow waters, beaches, and wetlands to deep-sea hydrothermal vents. collected and grown.
Bacteria, collectively known as purple bacteria, actually have a variety of colors, including yellow, orange, brown, and red, due to pigments related to the pigments that make tomatoes red and carrots orange.
They use a simpler photosynthetic system that utilizes a form of chlorophyll that absorbs infrared light and produces no oxygen, and they thrive in low-energy red or infrared light.
They were likely widespread on early Earth before the advent of plant-type photosynthesis, and may be particularly suited to planets orbiting cool red dwarfs, the most common type in the galaxy. there is.
“They are already thriving in certain areas here,” Dr. Coelho said.
“Imagine if they weren’t competing with green plants, algae, and bacteria. The red sun might give them the most favorable conditions for photosynthesis.”
After measuring the purple bacteria’s biological pigments and optical fingerprints, the researchers created a model of an Earth-like planet with varying conditions and cloud cover.
“In a variety of simulated environments, both wet and dry purple bacteria produced a dark-colored biosignature,” Dr. Coelho said.
“If purple bacteria thrive on the surface of frozen Earth, ocean worlds, snowball Earths, or modern Earth orbiting cooler stars, we have the tools to search for them. can do.”
team’s work will appear in Royal Astronomical Society Monthly Notices.
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Ligia Fonseca Coelho other. 2024. Purple is the new green. Spectrum of biological pigments and a purple world similar to the Earth. MNRAS 530 (2): 1363-1368; doi: 10.1093/mnras/stae601
Source: www.sci.news
