The color of life on Earth comes to mind. The vegetation that covers almost everything we encounter sparkles with this color thanks to chlorophyll, which produces oxygen and powers photosynthesis. But there are also some pigments whose host uses the materials and energies of its environment in a different way, which we can find in bacteria (as in this German lake).
The color of this chlorophyll, characteristic of bacteria, is often purple. In the early period of life on Earth, when there was almost no oxygen in our atmosphere, organisms could have created such a purple world, and it is easy to imagine that the situation is similar in other celestial bodies.
Különösen akkor lehet ez igaz, ha az adott bolygón nemcsak az oxigén hiányzik, de a látható fény sem túl sok, és helyette az infravörös sugárzás segíti az életet.
Newbie, that is MNRAS In a paper published in the journal, it was previously examined Cornell University Carl Sagan Institute A group led by a researcher asks how we might spot purple among signs of exoplanet life.
So, they examined terrestrial purple bacteria, and measured what they would look like while examining a color image of a distant planet, if life there also had that color. Such measurements have already been made in relation to green chlorophyll, but one should not think that all living planets are similar to ours, which is why researchers need to evaluate other possibilities.
A variety of bacteria in a laboratory at Cornell University.
Source: Ryan Young/Cornell University
“Bacteria can live well in a wide range of conditions, so they could easily be essential ingredients for life on many alien worlds,” said Ligia Fonseca Coelho, the research leader. “We need to create a database that ensures that our telescopes will not miss signs of life if they are not exactly like the ones that surround us every day,” added Lisa Kaltenegger, director of the institute and co-author of the study.
So far, astronomers have found more than 5,500 planets outside the solar system, including more than 30 planets similar to Earth, and giant telescopes in the future will subject them to more intense examination. Researchers list the different colors of terrestrial organisms and minerals and compile a catalog of them.
For this work, they cultured several purple bacteria, which, contrary to their name, can be not only purple, but also yellow, orange or even brown. What they have in common is that they can photosynthesize in low-energy red or even infrared light and do not produce oxygen in the process. According to the researchers, planets orbiting red dwarf stars, the most common type of star in our galaxy, may be particularly characteristic of this type of life activity.
Ligia F. Coelho, who led the research, identified purple water due to purple bacteria.
Source: Ryan Young/Cornell University
Based on the measurement data, the researchers also modeled how an exoplanet would color under the influence of purple bacteria under different conditions, and based on these calculations we already know what we will have to look for in future data from telescopes.
Carl Sagan marked Earth as a pale blue dot based on a Voyager image taken in 1990, where our planet is actually just a small blue dot. According to the researchers, if we wanted to observe a “pale purple dot” around a distant star, we would have to examine it closely, because there is a good chance that purple represents the color of life.
