Exoplanet Biosignatures: A Framework for Their Assessment.
The search for aliens in faraway worlds could be made easier, with new research determining a way to establish the difference between life and the illusion of life. The study focuses on the importance of 'biosignatures' in the atmospheres of exoplanets.
So far, we've found about 4,000 exoplanets, but the majority of those are big worlds like Neptune and Jupiter.We only know of about 160 planets that are Earth-sized or smaller, which we think is a prerequisite for finding an Earth-like planet. Of those, just 20 or so may have the potential to support life as we know it. Fortunately, exoplanet research technologies are improving.
So far, only the Viking mission has conducted a rigorous search for in situ biosignatures on another planet, focused on metabolic indicators of life, including the search for organic compounds (Biemann et al. 1977; Klein 1978).After a hiatus of more than four decades, a NASA mission concept is being developed—a Europa lander—whose top priority is the search for life (Hand et al. 2018).
The search for life has had a new enthusiastic restart in the last two decades thanks to the large number of new worlds discovered. The about 4100 exoplanets found so far, show a large diversity of planets, from hot giants to rocky planets orbiting small and cold stars. Most of them are very different from those of the Solar System and one of the striking case is that of the super-Earths.
To determine if the planet's atmosphere contains any biosignatures, which are chemical species that may indicate the presence of life, telescopes first measure the spectra of light radiated and reflected from the target planet. These spectra are then analysed to identify specific peaks in the infrared and visible regions. In the infrared region for example, peaks can be seen which indicate.
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The research field of exoplanets has grown dramatically since the first planet orbiting a Sun-like star was discovered nearly 20 years ago. Nearly 1000 exoplanets are known to orbit nearby stars, a few thousand more planet “candidates” have been identified, and planets are so common that on average every star in the Milky Way should have at least one planet ( 2, 3 ).