For the first time Methane and carbon dioxide found in atmosphere of habitable-zone exoplanet

We are not alone!

Uh, there is CO2 on this exoplanet! Should we be concerned about climate change? Maybe we have to rescue our brothers and sisters on this exoplanet? (Caution: Satire)

"The results are consistent with an ocean-covered surface underneath a hydrogen-rich atmosphere. The discovery provides a glimpse into a planet unlike anything else in our Solar System, and raises interesting prospects about potentially habitable worlds elsewhere in the Universe.
K2-18 b — which is 8.6 times as massive as Earth — orbits the cool dwarf star K2-18 in the habitable zone and lies 110 light years from Earth in the constellation of Leo. A first insight into the atmosphere of  K2-18 b came from observations with the Hubble Space Telescope but the atmospheric composition has been a subject of debate. The same researchers studied K2-18 b in 2020 and 2021, and identified it as belonging to a new class of habitable exoplanets called ‘Hycean’ worlds which could accelerate the search for life elsewhere. This prompted them to take a more detailed look with JWST, Hubble’s successor. ..."

From the abstract:

"The search for habitable environments and biomarkers in exoplanetary atmospheres is the holy grail of exoplanet science. The detection of atmospheric signatures of habitable Earth-like exoplanets is challenging due to their small planet-star size contrast and thin atmospheres with high mean molecular weight. Recently, a new class of habitable exoplanets, called Hycean worlds, has been proposed, defined as temperate ocean-covered worlds with H2-rich atmospheres. Their large sizes and extended atmospheres, compared to rocky planets of the same mass, make Hycean worlds significantly more accessible to atmospheric spectroscopy with the JWST. Here we report a transmission spectrum of the candidate Hycean world, K2-18 b, observed with the JWST NIRISS and NIRSpec instruments in the 0.9-5.2 μm range. The spectrum reveals strong detections of methane (CH4) and carbon dioxide (CO2) at 5σ and 3σ confidence, respectively, with high volume mixing ratios of ~1% each in a H2-rich atmosphere. The abundant CH4 and CO2 along with the non-detection of ammonia (NH3) are consistent with chemical predictions for an ocean under a temperate H2-rich atmosphere on K2-18 b. The spectrum also suggests potential signs of dimethyl sulfide (DMS), which has been predicted to be an observable biomarker in Hycean worlds, motivating considerations of possible biological activity on the planet. The detection of CH4 resolves the long-standing missing methane problem for temperate exoplanets and the degeneracy in the atmospheric composition of K2-18 b from previous observations. We discuss possible implications of the findings, open questions, and future observations to explore this new regime in the search for life elsewhere."

Methane and carbon dioxide found in atmosphere of habitable-zone exoplanet An international team of astronomers led by the University of Cambridge has used data from the NASA/ESA/CSA James Webb Space Telescope to discover methane and carbon dioxide in the atmosphere of K2-18 b, an exoplanet in the ‘Goldilocks zone’. This is the first time that carbon-based molecules have been discovered in the atmosphere of an exoplanet in the habitable zone.

Carbon-bearing Molecules in a Possible Hycean Atmosphere (open access)