These findings, including low ammonia, suggest an ocean under a hydrogen-rich atmosphere on K2-18, an exoplanet 8.6 times Earth’s mass, orbiting the dwarf star K2-18 in the habitable zone, 120 light-years away.
JWST has detected signs of methane and carbon dioxide in the atmosphere of K2-18. It’s a discovery that could help reshape the way we think about the search for life beyond Earth, and take our understanding of sub-Neptunes to the next level.
In 2021, an international collaboration led by Nikku Madhusudhan at the University of Cambridge to use JWST to take another peak at K2-18. Their team detected something extraordinary, methane, carbon dioxide, and potentially dimethyl sulfide, a compound that’s primarily created on Earth by living creatures. Now don’t get too excited. We’re not saying that there’s life there.
There needs to be more observations to absolutely confirm dimethyl sulfide AND they must eliminate non-life pathways that this could happen.
A few decades ago, we were just beginning to find exoplanets. We were doing it one transit at a time. The Kepler, and TESS, and all of these other telescopes start working and now there are over 5,500 exoplanets. Now we can look at their atmospheres and see clearly what’s going on with them, all this distance away.
We really need 16 JWSTs to follow up on all of the things that need closer observation.
Sub-Neptunes are the most common type of world that we have detected in our galaxy. Is that a consequence of our detection methods, or is it actually the case that it’s the most common type of world?
Nextbigfuture believes it is a consequence of not having good telescopes to find the smaller worlds.
Most exoplanets have been discovered with the transit technique.
We know that there’s a lot of methane in the atmosphere of K2-18. We see a lot of methane or we see a lot of methane absorption and strong detection there. But the fact that the JWST data basically didn’t find strong evidence of water in the atmosphere, that could indicate a couple things. It could indicate that maybe there is no ocean, there’s no water evaporating on a regular cycle, or maybe the ocean is not water. It could be something else. So those are a couple factors. Or maybe the ocean is frozen solid, and it’s also not evaporating into the atmosphere, and you’re having a lot of water transition and a water cycle like we do here on Earth. So it could mean there’s no ocean, could mean it’s frozen. It could mean that maybe it’s an ocean like liquid methane or liquid something else.
On Earth, dimethyl sulfide is only the byproduct of some kind of plankton. However, we do not know that on another planet if there is some non-plankton way of getting dimethyl sulfide.
Knicole Colón, the telescope’s deputy project scientist for exoplanet science. “It is anticipated that JWST observations may lead to the initial identification of potential biosignatures that could make habitability more or less likely for a given exoplanet. Future missions will be needed to conclusively establish the habitability of an exoplanet.”
This means that it is evidence consistent with the conclusion of a biosignature BUT that would be so huge a discovery and it is only a line on a spectrometer. There must be more observation to confirm.
They expect more papers written up where the biosigniture itself is proven to 99.9999% certainty. Right now it is may 99% certain. They would want to make the dimethyl sulfide reading rock solid. They then must work on eliminating other possibilities for the source and get more evidence in the atmosphere to confirm it is from alien life.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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There is a sulphur ecology around deep sea thermal vents. The pressure and density may make this competitive under the exoplanet’s ambient conditions.
For a science fiction treatment try Hal Clement’s “Iceworld.”
Do we have any idea how old the star system is? Also, wonder how much of the surface is liquid covered?
Cool if we find evidence of life, even primitive stuff, but we all know that what we really want to hear about is a planet that gained life billions of years ago, produced something that can think and manipulate (not Orcas), developed tools, the scientific method, and technology, and that we can talk to with a delay not measured in millenia . . . or the complete absence of same.
Unless I’m mistaken, the non-detection of water vapour does not rule out a liquid water ocean. It simply means an atmosphere not dominated by water vapour or steam, which is a good thing. The Earth’s atmosphere, at that distance, would also show no signal of water vapour.