SubNeptune planet K2-18b shows methane and dimethyl sulfide

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Discussion Overview

The discussion centers around the recent findings from NASA’s James Webb Space Telescope regarding the exoplanet K2-18b, specifically the detection of methane, carbon dioxide, and potentially dimethyl sulfide (DMS) in its atmosphere. Participants explore the implications of these findings, including the possibility of a subsurface ocean and the conditions of the planet's atmosphere.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants highlight the detection of methane and carbon dioxide on K2-18b, suggesting it supports the hypothesis of a water ocean beneath a hydrogen-rich atmosphere.
  • Others note the potential detection of dimethyl sulfide (DMS), which on Earth is associated with biological processes, raising questions about the possibility of life.
  • A participant questions whether there is sufficient data to determine if K2-18b is tidally locked, referencing the compact nature of red dwarf systems and comparing it to the TRAPPIST-1 system.
  • Concerns are raised about the orbital period of K2-18b and its implications for tidal locking, with a specific mention of its 32.940-day orbital period.

Areas of Agreement / Disagreement

Participants express excitement about the findings, but there is uncertainty regarding the implications of the data, particularly concerning tidal locking and the conditions on K2-18b. Multiple competing views remain on the significance of the findings and their interpretation.

Contextual Notes

The discussion reflects limitations in the current understanding of K2-18b's mass, its host star's mass, and their separation, which are necessary to fully assess tidal locking. There are also unresolved questions regarding the implications of the detected molecules.

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TL;DR
SubNeptune planet 120ly away shows presence of molecules associated with life
"A new investigation with NASA’s James Webb Space Telescope into K2-18 b, an exoplanet 8.6 times as massive as Earth, has revealed the presence of carbon-bearing molecules including methane and carbon dioxide.
...
The abundance of methane and carbon dioxide, and shortage of ammonia, support the hypothesis that there may be a water ocean underneath a hydrogen-rich atmosphere in K2-18 b. These initial Webb observations also provided a possible detection of a molecule called dimethyl sulfide (DMS). On Earth, this is only produced by life. The bulk of the DMS in Earth’s atmosphere is emitted from phytoplankton in marine environments."

https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b
 
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Very thrilling and exciting! :smile:
 
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Raises an eyebrow, a la Mr. Spock. "Fascinating!"Seriously though, do we have enough data on the exoplanet's mass, it's host star's mass and their separation to know whether K2-18b is tidally locked?

From popular science articles I've read (Sky & Telescope, I think) tidal locking is a problem for exoplanets orbiting red dwarves because these systems tend to be far more compact than our, more extended retinue of planets.

https://en.wikipedia.org/wiki/TRAPPIST-1

Several of the planets in the Trappist-1 system are expected to be tidally locked and I note that the outermost has an orbital period of 18.772 days. The cited period for K2-18b is 32.940 days. I wonder if that's sufficiently distant to place it outside of the tidal locking zone?

Any thoughts?Thank you,

Cerenkov.
 
Stinky.
 
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