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posted by martyb on Thursday September 02 2021, @03:04AM   Printer-friendly

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.

Hycean planet.

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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  • (Score: 0) by Anonymous Coward on Thursday September 02 2021, @03:10AM (1 child)

    by Anonymous Coward on Thursday September 02 2021, @03:10AM (#1173541)

    Let's aim for one of the badboys.

    • (Score: 0) by Anonymous Coward on Thursday September 02 2021, @03:36AM

      by Anonymous Coward on Thursday September 02 2021, @03:36AM (#1173556)

      Mars just got friendzoned. Will it attempt a musky ladder jump?

  • (Score: 4, Insightful) by c0lo on Thursday September 02 2021, @03:14AM (6 children)

    by c0lo (156) on Thursday September 02 2021, @03:14AM (#1173545) Journal

    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.

    Ummm... in my mind, there's a difference between "capable of sustaining some kind of life" vs "habitable by humans".
    I don't remember anything about humans living their everyday life in "the more extreme aquatic environments on our planet".

    --
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    • (Score: 2) by c0lo on Thursday September 02 2021, @03:30AM (4 children)

      by c0lo (156) on Thursday September 02 2021, @03:30AM (#1173553) Journal

      Reading TFSciAbstract, I got it. The guys say there could exist such planets sustaining a local life (to generate some oxygen that humans need for breathing) and having at least some zones where humans can live (assuming they are OK to float while doings so).

      We show that Hycean planets can be significantly larger compared to previous considerations for habitable planets, with radii as large as 2.6 R⊕ (2.3 R⊕) for a mass of 10 M⊕ (5 M⊕). We construct the Hycean habitable zone (HZ), considering stellar hosts from late M to Sun-like stars, and find it to be significantly wider than the terrestrial-like HZ. While the inner boundary of the Hycean HZ corresponds to equilibrium temperatures as high as ∼500 K for late M dwarfs, the outer boundary is unrestricted to arbitrarily large orbital separations. Our investigations include tidally locked "Dark Hycean" worlds that permit habitable conditions only on their permanent nightsides and "Cold Hycean" worlds that see negligible irradiation.

      2.6 R⊕ at 10 M⊕ gets a wee under 1.5g at the surface.
      A thicker atmosphere extends the distance to the outer limit of the Goldilocks zone - so higher chances to discover habitable conditions when looking for ocean worlds than when looking for smaller but denser rocky planets.

      (fucking sci journos and their "translation")

      --
      https://www.youtube.com/watch?v=aoFiw2jMy-0
      • (Score: 3, Insightful) by takyon on Thursday September 02 2021, @04:04AM (2 children)

        by takyon (881) <takyonNO@SPAMsoylentnews.org> on Thursday September 02 2021, @04:04AM (#1173561) Journal

        "Potentially habitable exoplanets" is understood to be a broad term, including plenty of planets that would be bad vacation spots for humans. Some of the candidates might be being blasted clean by red dwarf radiation. I don't think atmospheric oxygen is a required characteristic, just liquid water.

        Interestingly, this list over here [wikipedia.org] already includes planets at up to 2.5 Earth radii (only up to 6.98 Earth masses, for LHS 1140 b [wikipedia.org], but the masses for the planets above 2 Earth radii are unknown or need to be updated).

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        • (Score: 2) by c0lo on Thursday September 02 2021, @04:18AM

          by c0lo (156) on Thursday September 02 2021, @04:18AM (#1173564) Journal

          "Potentially habitable exoplanets" is understood to be a broad term

          [Citation needed] to correct my understanding.
          No seriously, I'll be grateful for one.

          --
          https://www.youtube.com/watch?v=aoFiw2jMy-0
        • (Score: 2) by c0lo on Thursday September 02 2021, @04:43AM

          by c0lo (156) on Thursday September 02 2021, @04:43AM (#1173569) Journal

          Corrections to my understanding of the term [wikipedia.org]

          Planetary habitability is the measure of a planet's or a natural satellite's potential to develop and maintain environments hospitable to life.[1] Life may be generated directly on a planet or satellite endogenously or be transferred to it from another body, through a hypothetical process known as panspermia.[2] Environments do not need to contain life to be considered habitable nor are accepted habitable zones the only areas in which life might arise.[3]

          * Life in general, not just human life.
          * Life is not a requirement for habitability.

          --
          https://www.youtube.com/watch?v=aoFiw2jMy-0
      • (Score: 2) by Freeman on Thursday September 02 2021, @01:47PM

        by Freeman (732) Subscriber Badge on Thursday September 02 2021, @01:47PM (#1173688) Journal

        Yet, the atmosphere could contain enough concentrations of something toxic to humans that it would be essentially uninhabitable.

        --
        Joshua 1:9 "Be strong and of a good courage; be not afraid, neither be thou dismayed: for the Lord thy God is with thee"
    • (Score: 2) by HiThere on Thursday September 02 2021, @01:37PM

      by HiThere (866) on Thursday September 02 2021, @01:37PM (#1173684) Journal

      Yes, and I've got another candidate variety with no known entries:
      Large planets (well, up to a couple of Earth masses) with enough internal radiation to maintain liquid water at the surface even though they are floating free of any sun. Of course, the only life they could host would live off the energy of radiation, possibly some chemical energy eaters, but those would depend on the radiation eaters to provide their sustenance. And on Earth that means I'm only talking about microbes...so that may be all that would be possible. But it's life.

      --
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  • (Score: 0) by Anonymous Coward on Thursday September 02 2021, @03:31AM

    by Anonymous Coward on Thursday September 02 2021, @03:31AM (#1173554)

    This places them somewhere between Earth and giant planets like Neptune or Uranus.

    I know which end I prefer... hehehe

    Dang, who farted?

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