Astronomers using the James Webb Space Telescope have found sulfur-containing molecules on an exoplanet, which on Earth are only formed by the activity of organisms. They were found on a planet eight times larger than Earth and orbiting a star 124 light-years away. Potential signs of life have previously been found on this planet, but their presence has never been confirmed. Research published in The Astrophysical Journal Letters.
The exoplanet K2-18b, which astronomers are studying, is a sub-Neptunian, meaning it has a smaller mass or radius than Neptune. It is located in the habitable zone around its star, K2-18, which is a red dwarf with a diameter at least one-third that of the Sun. The planet has previously been found to have traces of a liquid ocean, as well as carbon dioxide and methane, which could be the basis for the creation of larger organic compounds.
Scientists also found dimethyl sulfide on the planet, which is formed on Earth as a result of the vital activity of seaweed, which could indicate the presence of life on K2-18b. However, the observations of scientists at that time did not have sufficient statistical significance, that is, they were not precise enough to claim the existence of compounds originating from living organisms. So a team of British and American scientists, led by specialists from the University of Cambridge, used the James Webb to more precisely determine the composition of the atmosphere of this planet.
The scientists were able to detect a distinct signal of dimethyl sulfide in the planet's atmosphere, i.e. one that exactly belongs to this compound. In addition, the researchers found a related compound, dimethyl disulfide, which is also formed on Earth by the activities of living organisms.
The scientists found that these compounds are present in the atmosphere of K2-18b at concentrations of about 10 parts per million, or 10 dimethyl sulfide or dimethyl disulfide per million air molecules. This is a thousand times higher concentration than in Earth's atmosphere, which could indicate greater biological activity on the planet.
The scientists believe their finding needs further confirmation with further observations by the James Webb Space Telescope. So far, their measurements have an accuracy of only 3,4 sigma, which is equivalent to a 3 in 1000 chance of error. To definitively confirm the presence of compounds originating from living organisms, an accuracy of five sigma is needed, or a XNUMX in XNUMX million chance of error.
Furthermore, even the detection of dimethyl sulfide and dimethyl disulfide does not mean that there is life on K2-18b. Last year, a team of scientists found traces of these molecules on a comet, which could indicate that they could have formed in space. So to confirm their results, the scientists will also need to rule out the possibility that dimethyl sulfide was brought to the planet by comets that have collided with it.
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