James Webb Space Telescope could find signs of life on alien 'hycean' ocean worlds.

Hycean worlds, which are a possible kind of exoplanet with deep oceans surrounded by a thick envelope of hydrogen, could provide the best chance for the James Webb Space Telescope (JWST) to detect biosignatures, according to a new study.

Those potential signs of life are a group of chemicals called methyl halides, which on Earth are produced by some bacteria and ocean algae.

For now, the existence of hycean planets remains hypothetical. Their name is a portmanteau of "hydrogen" and "ocean," first coined in 2021 by planetary scientist Nikku Madhusudhan of the University of Cambridge.

Hycean planets are expected to orbit red dwarf stars, and the best candidate for a hycean world is the planet K2-18b. This exoplanet, which is categorized as a "sub-Neptune" world, orbits in the habitable zone of a red dwarf star 124 light-years from Earth in the constellation of Leo, the Lion.

The Hubble Space Telescope discovered water vapor in K2-18b's atmosphere in 2019, and JWST has detected the presence of carbon dioxide and methane in the planet's atmosphere, along with a lack of carbon monoxide and ammonia — exactly as predicted by the hycean planet hypothesis. There's also tentative evidence that a compound called dimethyl sulfide, which on Earth is only produced by ocean plankton, also exists in K2-18b's atmosphere, but this evidence continues to prove contentious.

Source: www.space.com

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