Purple Signs of LifeAstrobiologists examine purple microorganisms as a possible link to life on early Earth and other planets. Image source: CNN
A story published in CNN takes a look at the color purple and how astrobiologists are considering the possible connection between purple organisms and the evolution of life on early Earth and other planets.
The Purple Earth hypothesis, first presented by microbiologist Shil Dassarma at the University of Maryland School of Medicine, suggests that ancient microbes may have relied on retinal rather than chlorophyll to harness energy from sunlight. Retinal is easier to produce in low-oxygen environments and, because it absorbs green light and reflects a combination of red and violet, makes the organism appear purple. The pigment is evident in halophiles—salt-loving extremophiles—found on Earth today.
Purple-colored bacteria can also be found forming mats deep below in less-salty lake environments, and it is possible too that their ancient ancestors may have been widespread and detectable from Earth’s surface.
The hypotheses could extend to other planets. A new paper, “Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life” published in August 2017, considers the detection of purple as one possible indicator of evolving life in the search for habitable exoplanets. The research and collaboration for the study outlining the numerous categories of biosignatures was supported by the NASA Astrobiology Program, the Nexus for Exoplanet System Science (NExSS), the NASA Postdoctoral Program (NPP), the NASA Astrobiology Institute (NAI), and NASA Exobiology.
Read the article “Purple Life Beyond Earth” at CNN.
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