When astronomers search for exoplanets, they’re not only trying to confirm if they exist — but they’re also trying to see if they can support life as we know it. That’s because identifying exoplanets is a fundamental part in the international search for extraterrestrial life.
As explained by NASA, astronomers often look to see if planets are in the so-called “habitable zone.” This is defined by the distance between a star and an exoplanet where liquid water could hypothetically exist on an exoplanet’s surface. This is frequently also referred to as the Goldilocks’ zones, where conditions can’t be too hot nor too cold for life. As it stands, only 67 out of nearly 5,000 exoplanets are potentially habitable worlds. Of these exoplanets, only 28 are more likely to be rocky planets, which is an indicator that there could be water on its surface like Earth.
However, a new discovery in our own solar system is nudging some astronomers to rethink how habitability should be defined. Last month, in a study published in the journal Nature Astronomy, astronomers said there is strong evidence on Saturn's moon Enceladus of the presence of hydrogen cyanide, which is an essential molecule in forming amino acids and therefore one of the most basic ingredients in life. In addition to hydrogen cyanide, the researchers found that many of the organic compounds in the plumes were oxidized, which suggests that there could be multiple pathways to sustain life in the moon’s subsurface ocean.
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