"Hycean Worlds" Identified as Possible Habitable Exoplanets
takyon writes:
Hycean Planets Might Be Habitable Ocean Worlds
According to the researchers, Hycean worlds could greatly accelerate the search for life elsewhere. In some ways they are reminiscent of Earth, largely or even completely covered by oceans. Yet they are also uniquely alien: up to 2.6 times the diameter of Earth, with temperatures up to 200 degrees C (about 400 degrees F) and thick hydrogen atmospheres. This places them somewhere between Earth and giant planets like Neptune or Uranus.
[...] How, then, might Hycean planets be habitable? Having plentiful liquid water is of course a good start. These planets, unlike most mini-Neptunes, may have solid surfaces, like Earth. Many of the known Hycean candidates are larger and hotter than Earth, but still would be able to host large oceans, the researchers say. The conditions might be similar to some of the more extreme aquatic environments on our planet, but could theoretically still support at least microbial life.
[...] So, how would astronomers look for evidence of life on any of these worlds? They will search for biosignatures, chemical fingerprints of biological processes in the planets' atmospheres. Some common ones are oxygen, ozone, methane and nitrous oxide, as well as methyl chloride and dimethyl sulphide. The last two are not common on Earth, but might be on hydrogen-rich planets.
[...] Madhusudhan and his team say that many of these biosignatures should be easily detectable on Hycean planets. In fact, the nature of the planets themselves - larger sizes, higher temperatures and hydrogen-rich atmospheres - means that the biosignatures would be even more easily detectable than on Earth-like planets.
Also at ScienceAlert and Syfy Wire.
Journal Reference:
Nikku Madhusudhan, Anjali A. A. Piette, Savvas Constantinou. Habitability and Biosignatures of Hycean Worlds - IOPscience, The Astrophysical Journal (DOI: 10.3847/1538-4357/abfd9c, arXiv)
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