Scientists find strongest evidence yet of life on an alien planet

WASHINGTON, April 16 (Reuters) – In a potential landmark discovery, scientists using the James Webb Space Telescope have obtained what they call the strongest signs yet of possible life beyond our solar system, detecting in an alien planet’s atmosphere the chemical fingerprints of gases that on Earth are produced only by biological processes.

The two gases – dimethyl sulfide, or DMS, and dimethyl disulfide, or DMDS – involved in Webb’s observations of the planet named K2-18 b are generated on Earth by living organisms, primarily microbial life such as marine phytoplankton – algae.

This suggests the planet may be teeming with microbial life, the researchers said. They stressed, however, that they are not announcing the discovery of actual living organisms but rather a possible biosignature – an indicator of a biological process – and that the findings should be viewed cautiously, with more observations needed.

Nonetheless, they voiced excitement. These are the first hints of an alien world that is possibly inhabited, said astrophysicist Nikku Madhusudhan of the University of Cambridge’s Institute of Astronomy, lead author of the study published in the Astrophysical Journal Letters.

“This is a transformational moment in the search for life beyond the solar system, where we have demonstrated that it is possible to detect biosignatures in potentially habitable planets with current facilities. We have entered the era of observational astrobiology,” Madhusudhan said.

Madhusudhan noted that there are various efforts underway searching for signs of life in our solar system, including various claims of environments that might be conducive to life in places like Mars, Venus and various icy moons.

K2-18 b is 8.6 times as massive as Earth and has a diameter about 2.6 times as large as our planet.
It orbits in the “habitable zone” – a distance where liquid water, a key ingredient for life, can exist on a planetary surface – around a red dwarf star smaller and less luminous than our sun, located about 124 light-years from Earth in the constellation Leo. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). One other planet also has been identified orbiting this star.

Full Report

Hmmm …

Previous, more tentative announcement in 2023
https://www.livescience.com/space/exoplanets/james-webb-telescope-sees-potential-signs-of-alien-life-in-the-atmosphere-of-a-distant-goldilocks-water-world

Here is a qualified rebuttal, of sorts.
https://iopscience.iop.org/article/10.3847/1538-4357/ad8565

ISOPEN ACCESS
Evidence for Abiotic Dimethyl Sulfide in Cometary Matter
Hänni et al

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Hmmmmmmmm….

No skerrick of natural abiotic dimethyl sulfide is found on earth. It can be produced in a lab of course but it is very much pushing enthalpy uphill.

The Hänni paper from last year has reanalysed spect data from 67P/Churyumov–Gerasimenko to determine whether the C2H6S detected was dimethyl sulfide or ethanethiol. Their analysis suggests it was more likely to be dimethyl sulfide tha ethanethiol.

This makes it something of a philosophical problem about assumptions and probability.

Hänni’s paper ends
“Our results provide the first evidence for the existence of an abiotic synthetic pathway to DMS in pristine cometary matter and hence motivate more detailed studies of the sulfur chemistry in such matter and its analogs. “

I’m trying to express the tension that exist in the following facts.

1/ There is no known or proposed natural abiotic synthesis path for dimethyl sulfide in a planetary environment.

2/ There IS a proposed natural abiotic synthesis path for ethanethiol, involving metal sulfides and ethylene, the later being rare in nature but not unknown.

3/ Hänni et al takes it as read that the organics on a comet are abiotic: not unreasonable but the chance that they are not needs to be taken into account

4/ all manner of organic compounds exist in space by random collisions by high energy particles that would not survive for a second in planetary environment with an atmosphere.

5/ the Hänni paper notes that the signature is more likely to be dimethyl sulfide but this is “local “ probability. A full assessment of all facts would produce a different probability.

We would need someone to put this into a Bayesian Matrix. I wish Brewer were here.