Light reflected from the surface of plant leaves, bacteria in air and water, and animals on the planet's surface could betray the presence of life on Earth's potential "twins" for a new generation of powerful telescopes, astronomers say in the journal Astrobiology.
After the launch of the Kepler orbiting telescope, scientists discovered almost two thousand planets outside the solar system, several dozen of which are potential "doubles" of the Earth or are in the so-called "life zone". Their discovery prompted planetary scientists and astrobiologists to start developing methods that would assess their suitability for life or try to find traces of it in their atmosphere.
Most of these methods, as noted by Edward Schwieterman of the University of Washington in Seattle (USA), are designed to detect traces of the life of plants and other photosynthetic organisms, which are the easiest way to find traces of life on Earth, looking at it from space.
Such techniques are based either on how plants change the chemical and isotopic composition of the atmosphere, or on traces of chlorophyll, the main photosynthetic pigment of flora, in the spectrum of the planet's atmosphere. For example, if a planet is covered with forests, then the light reflected from it will be noticeably brighter in the "red" part of the spectrum, since photosynthetic organisms will absorb the green component of visible light.
Schwieterman and his colleagues wondered if the light reflected from the molecules of other pigment molecules, which give color to all flora and fauna on Earth, could be used to detect them on the surface of exoplanets.
To do this, scientists studied the chemical structure and spectrum of several dozen pigments found in the covers of the most common algae and microbes, and tried to estimate, using a computer model of an exoplanet, how visible they will be to telescopes on Earth.
As these calculations showed, with a sufficiently high "density" of the population of the most common representatives of flora or fauna, traces of their pigments will be clearly visible in the general spectrum of the planet for a new generation of ground-based and space telescopes that are now being built on Earth.
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This is both good and bad news - this finding suggests that we will be able to detect them, but we will not be able to understand where such organisms are present. Nevertheless, according to Shviterman and his colleagues, this problem can be solved in principle - according to them, long enough observations of fluctuations in the spectrum of the potential "twin" of the Earth can provide enough data to determine where the carriers of this or that pigment live.
Now Schwieterman's group is working on creating a database of spectra of various representatives of flora and fauna on Earth, which, they hope, will help the under construction James Webb and TESS telescopes find traces of life on exoplanets already discovered and not yet known to us.
