The foundation of their method comes from a paper published in Astrobiology in 2016 in which a list of roughly 14,000 compounds likely to appear as gasses in the atmospheres of extrasolar planets’ is outlined. It also assumes that life in that set of observable exoplanets is rare and that living organisms tend to leave biosignatures in the planets they inhabit.Īlthough each of these assumptions can be questioned, it follows that if the chemical composition of a planet is unusual, then a possible cause of this unusual composition is that life exists on that planet.
While over 5,000 exoplanet candidates have been confirmed, scientists estimate that there are hundreds of billions of planets within the Milky Way alone. First that a given sample of exoplanets can be statistically representative of all the atmospheres in the universe. Still their argument does rest on a few core assumptions. “Our method circumvents this issue a bit by saying ‘let the data tell us what is anomalous.’” “There has been a long history in exoplanet research of people finding abiotic mechanisms that produce candidate biosignature gases,” says Kinney. In moving away from the assumption that the thread must be chemical, Kinney and Kempes hope to avoid some common pitfalls, namely abiotic processes that mimic biotic ones. “Conceptually, there must be some common thread between all things in the universe that we want to describe as being alive,” says Kinney, who co-authored the paper, published June 22 in Biology & Philosophy, outlining their theory. The parameters for ‘anomalousness’ should be data-dependent, rather than being based on assumptions about life that may be Earth-centric. Planets with peculiar atmospheres, relative to a representative sample, should be regarded as the most likely settings for extraterrestrial life. One of the most basic signs that an entity is an organism on Earth, that it produces carbon dioxide or water as a product of respiration or photosynthesis, may not apply as the universal indicator of life elsewhere in the cosmos. Some astrobiologists argue that we should be open to the possibility that extraterrestrial organisms could be very different to life as we know it. There are, however, certain problems with the biosignature method of detecting life on alien worlds. To fully realize the potential of the transit method in detecting possible life-supporting planets, astronomers must seek improvements in our technology for detecting and isolating the emission spectra of exoplanets.įortunately, NASA’s proposed FINESSE mission, the European Space Agency’s proposed Exoplanet Spectroscopy Mission, and the recently launched James Webb Space Telescope (JWST) will provide scientists with a look at many new potential homes for extraterrestrial life, as well as provide them with a vastly improved ability to analyze the emission spectra of exoplanets. That’s because they are much easier to spot and confirm, as these so-called hot Jupiters block more starlight more frequently than smaller, more distantly orbiting worlds.īut hot Jupiters are unlikely to be habitable locales for life - at least life as we know it. Since we know that certain biological processes on Earth leave chemical traces in our atmosphere, if we manage to identify those same traces in the atmospheres of other planets, then we would have good reason to believe living organisms inhabit or inhabited those other worlds.Ĭurrently, the transit method has been mostly used to analyze giant, hot planets that orbit very near their host stars. Analyzing this resulting emission spectra can provide astronomers with a detailed log of the chemistry likely present in the atmosphere of the alien world.Īstrobiologists who investigate the atmospheres of exoplanets this way are looking for what they call biosignatures, or chemical evidence for past or present life. Using a spectrograph, astronomers can separate that filtered starlight into its constituent components. When a distant star passes behind its exoplanet from the point of view of Earth, starlight filters through the atmosphere of the exoplanet before making its way to our instruments.
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