James Webb Telescope Sees Exoplanet Might Have Be covered With a Liquid Water Ocean

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NASA’s James Webb Space Telescope observed K2-18 b whic an exoplanet 8.6 times as massive as Earth. It is showing the presence of carbon-bearing molecules including methane and carbon dioxide. Webb’s discovery adds to recent studies suggesting that K2-18 b could be a Hycean exoplanet, one which has the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface.

The first insight into the atmospheric properties of this habitable-zone exoplanet came from observations with NASA’s Hubble Space Telescope, which prompted further studies that have since changed our understanding of the system.

K2-18 b orbits the cool dwarf star K2-18 in the habitable zone and lies 120 light-years from Earth in the constellation Leo. Exoplanets such as K2-18 b, which have sizes between those of Earth and Neptune, are unlike anything in our solar system. This lack of equivalent nearby planets means that these ‘sub-Neptunes’ are poorly understood, and the nature of their atmospheres is a matter of active debate among astronomers.

The suggestion that the sub-Neptune K2-18 b could be a Hycean exoplanet is intriguing, as some astronomers believe that these worlds are promising environments to search for evidence for life on exoplanets.

While K2-18 b lies in the habitable zone, and is now known to harbor carbon-bearing molecules, this does not necessarily mean that the planet can support life. The planet’s large size — with a radius 2.6 times the radius of Earth — means that the planet’s interior likely contains a large mantle of high-pressure ice, like Neptune, but with a thinner hydrogen-rich atmosphere and an ocean surface. Hycean worlds are predicted to have oceans of water. However, it is also possible that the ocean is too hot to be habitable or be liquid.

“Although this kind of planet does not exist in our solar system, sub-Neptunes are the most common type of planet known so far in the galaxy,” explained team member Subhajit Sarkar of Cardiff University. “We have obtained the most detailed spectrum of a habitable-zone sub-Neptune to date, and this allowed us to work out the molecules that exist in its atmosphere.”

4 thoughts on “James Webb Telescope Sees Exoplanet Might Have Be covered With a Liquid Water Ocean”

  1. Most larger planets in our solar system have sizable moons.

    I wonder if a spectral analysis like this with a temporal filter of some kind could show a “monthly” variation in some lines indicating they come from a.moon rather than the planet.

    Or would any signal be swamped out be the planet?

    Just a thought

  2. This reminds me somewhat of the ocean world from “Interstellar”. Of course, that was more Earth sized and the gravity on this planet would like crush us. I need to look up how hot is too hot to support life. Seems like it’d have to be near boiling, since life can survive in some extreme places, even here.

  3. “Although this kind of planet does not exist in our solar system, sub-Neptunes are the most common type of planet known so far in the galaxy . . .”

    Aha. And these giant water planets eventually develop enormously hungry and dangerous lifeforms that, though non-sentient, eventually spread to any other planet in the star system also possessing liquid water, where this invasive species overwhelms most existing lifeforms, that were developed in a less challenging environment.

    Thus the real reason for the Fermi Paradox is unveiled. Thank goodness we didn’t have one of these planets here.

  4. They also found a potential biosignature on that planet, dimethyl sulfide, which, on Earth at least, is produced mostly by sealife.

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