Scientists find strongest evidence yet of life on an alien planet; Webb sees 3-sigma evidence for dimethyl sulfide

[Hans Blaster]

On the subject of exoplanets, the pop-sci press generally deviate from the scientific publications by focusing more on the sensationalist aspect of looking for life forms.
As this thread has revealed, the scientific objective is to have a confidence level the so called biosignatures are real and not some statistical anomaly.

The paper itself mentions "life" three times.

In the introduction (on background):

"The Hycean paradigm developed in recent years has
the potential to significantly expand and accelerate the
search for life elsewhere."

And referencing other studies:

"Another potential indication of
biological activity was suggested by a weak (≲2-σ) infer-
ence of dimethyl sulfide (DMS) in K2-18 b with previous
JWST observations (Madhusudhan et al. 2023b).
The tentative inference of DMS in K2-18 b opens an
important debate on the possible presence of life on K2-
18 b. "

And in the discussion at the end:

"The spectrum shows multiple spectral features between
∼6-11 μm which are best explained
by a combination of DMDS and DMS in the atmosphere,
both molecules uniquely produced by life on Earth and
predicted as promising biosignatures in habitable exo-
planets".


"Their [DMDS and DMS] identification [in theory papers] as robust
biosignatures is due to the fact that on Earth, both
molecules are uniquely produced by life (particularly
marine biota) in small quantities of ≲1 ppb by volume
and are not supplied by abiotic photochemistry. Never-
theless, here we explore some potential alternatives."

The direction technology needs to take are straightforward to go from a three sigma to a five sigma level or reveal the anomaly.

A current limitation is the light reaching the spectrometers is polluted with starlight combined with light reflected from the exoplanets or passing through their atmospheres.

This was a transmission spectroscopy study.

To alleviate this limitation is to build larger telescopes which are in the pipeline. Larger telescopes not only collect more light but are theoretically able to resolve stars into disks which appear as point sources in smaller telescopes. This allows starlight to be filtered out before it reaches the spectrometer.

The two methods being researched are using coronagraphs which are smaller telescopes built inside the earth or space based telescope.
The other is the use of starshades which are spacecraft placed thousand of kilometres in front of the telescope and use petal shaped obstructions designed to minimise diffraction and to create a deep shadow on the telescope optics.
Both methods will greatly increase the S/N ratio.

There is some planet exploring mission that is now at risk due to proposed budget cuts, but I don't remember the name of it.

 

[SelfSim]

Just a group response to @sjastro and @Hans Blaster here .. (other comments on this sub-discussion also welcome).

Ok .. so in accepting the technology development advice(s) presented, I weakened my stance on the notion of the infeasibility of remote telescopic sensing of potential exo-life. I went looking for something I remembered from past discussions on this same topic and I found a very recent paper which details what looks to be a plausible technique.

The paper is: Remote Detection of Red Edge Spectral Characteristics in Floating Aquatic Vegetation, (Murakami etal, Astrobiology, March 2025, E-pub: Jan 2024), my emboldenments added for summarisation purposes:

The vegetation red edge of terrestrial plants is a key biosignature for the detection of life on Earth-like habitable exoplanets. Although water is essential for plants, an excess of water can limit the distribution of terrestrial vegetation. On planets with extensive water coverage and limited land, floating vegetation on the water’s surface could serve as a crucial indicator of life. This study examined the spectral reflectance of floating plants across various scales, from individual leaves to lake-wide vegetation coverage.

Analysis by different possible scenarios:

Our comparisons between individual leaves revealed that the red edge of floating plants was equivalent to or even more pronounced than that of terrestrial plants. Although water can reduce plant reflectance, the naturally low reflectance of water enhances the detection sensitivity for floating vegetation. Our observations of seasonal changes, such as the proliferation of floating plants in summer and their decline in winter, revealed significant variations in lake reflectance.

Their technique:

By analyzing satellite images of lakes and marshes over a 5-year period, we confirmed that these seasonal variations in reflectance reliably indicated the presence of floating vegetation. The seasonal signal showed robustness to the effects of clouds, which pose another challenge on water-rich planets. We propose that floating vegetation be considered alongside, or even in place of, terrestrial vegetation in the search for extraterrestrial life.

They're proposing how JWST and ground based scope can be used can be used for detection:

Ongoing follow-up observations by the latest space telescope, James Webb Space Telescope (JWST), and ground-based telescopes are clarifying the planetary environments and their habitability. In the next decade, we anticipate achieving direct imaging of habitable planets (Fitzgerald et al., 2022), potentially enabling the detection of signs of life for the first time. Currently, the primary targets of biosignature surveys are habitable planets around M-dwarfs, smaller stars with lower temperatures than the Sun, and the most abundant stellar type in the universe (Scalo et al., 2007). Observing exoplanets around M-dwarfs provides valuable insights into planetary environments through transit spectroscopy, which enables the characterization of atmospheric composition.

Looks like Evolution plays a fundamental role in their assumptions too:

Our research has shown that the red edge, previously considered an indicator specific to terrestrial vegetation, can also be detected in vegetation over water. This finding has significant implications for future exoplanet surveys; it suggests that floating plants could be a viable target in the search for life on water-rich exoplanets. To produce a detectable signature from exoplanets, exo-floating plants would need to acquire morphology that improves surface tension and buoyancy. These fundamental traits would likely be acquired after plants invade land on an Earth-like terrestrial planet. On an oceanic planet, it remains uncertain whether plants can develop such traits while remaining in the water. Although floating plants currently inhabit local freshwater environments on Earth, their global proliferation in oceans could be conceivable on an exoplanet, as illustrated by the Azolla event hypothesis.

An interesting and quite up-to-date study!

I feel a litle more reassured in the sanity of this version of 'the hunt' for exo-life.

 

[sjastro]

Just a group response to @sjastro and @Hans Blaster here .. (other comments on this sub-discussion also welcome).

Ok .. so in accepting the technology development advice(s) presented, I weakened my stance on the notion of the infeasibility of remote telescopic sensing of potential exo-life. I went looking for something I remembered from past discussions on this same topic and I found a very recent paper which details what looks to be a plausible technique.

The paper is: Remote Detection of Red Edge Spectral Characteristics in Floating Aquatic Vegetation, (Murakami etal, Astrobiology, March 2025, E-pub: Jan 2024), my emboldenments added for summarisation purposes:


Analysis by different possible scenarios:

Their technique:

They're proposing how JWST and ground based scope can be used can be used for detection:

Looks like Evolution plays a fundamental role in their assumptions too:

An interesting and quite up-to-date study!

I feel a litle more reassured in the sanity of this version of 'the hunt' for exo-life.

I had a look at the Fitzgerald link which exemplifies how technology is driving the research on exoplanets.
In my previous post I mentioned coronagraphs which as the name implies where initially designed to screen out the Sun's body to make the solar corona visible.

The early coronagraphs were extremely simple which can be built by any skilful amateur astronomer.

​

The Fitzgerald link shows the status of the PSI (Planetary Systems Imager) under development where coronagraphs are part of a modular system.
I have taken excerpts from the link such as the various project objectives of which the search for extra-terrestrial life is one of them.

​

 

[linux.poet]

MOD HAT ON​

This thread has been cleaned of a goading post and its responses.​

MOD HAT OFF​

 

[SelfSim]

I had a look at the Fitzgerald link which exemplifies how technology is driving the research on exoplanets.
In my previous post I mentioned coronagraphs which as the name implies where initially designed to screen out the Sun's body to make the solar corona visible.

The early coronagraphs were extremely simple which can be built by any skilful amateur astronomer.

View attachment 363919
​

The Fitzgerald link shows the status of the PSI (Planetary Systems Imager) under development where coronagraphs are part of a modular system.
I have taken excerpts from the link such as the various project objectives of which the search for extra-terrestrial life is one of them.

View attachment 363920

​

Hmm .. interesting .. although I'm glad I won't have to build it .. I'm sure its a super-clever design but it'd take me the full ten years until its expected to imaging exo-planets, just for me to begin to understand it(!?)

I really hope it doesn't get derailed by the Marauder-In-Chief and/or one of his cohorts!

That being said, I can see this technology paving the way forward in terms of providing data to constrain the speculations and narrowing the playing field amongst the thousands (maybe tens-of-thousands) of verified exoplanets over the next 10 years.

I'm still not sure this will produce the results the Star Trek Universe viewing audience is expecting though ..

 

[AV1611VET]

Just fyi, saltes:

But both Hänni and Browne conducted recent research that showed it would be a stretch to rely on dimethyl sulfide as a conclusive sign of life.

SOURCE

And also, from the same source:

Both researchers emphasize that scientists don’t know nearly enough about K2-18 b to determine whether any dimethyl sulfide found in its atmosphere was produced by living organisms—or by abiotic happenstance of the kind that led to their own observations. Researchers don’t even know whether the compound would disappear as rapidly as it does in Earth’s nitrogen-rich atmosphere, given that the alien world’s atmosphere is dominated by carbon dioxide instead.

“Chemistry and the planets and all of those processes are so diverse,” Browne says. “There’s always going to be a way to make something abiotically.”

 

[sjastro]

Hmm .. interesting .. although I'm glad I won't have to build it .. I'm sure its a super-clever design but it'd take me the full ten years until its expected to imaging exo-planets, just for me to begin to understand it(!?)

I really hope it doesn't get derailed by the Marauder-In-Chief and/or one of his cohorts!

That being said, I can see this technology paving the way forward in terms of providing data to constrain the speculations and narrowing the playing field amongst the thousands (maybe tens-of-thousands) of verified exoplanets over the next 10 years.

I'm still not sure this will produce the results the Star Trek Universe viewing audience is expecting though ..

The correct terminology is the Commander in Chief of the Grand Assembly of Imbeciles as highlighted in another thread with tariffs imposed on the activities of penguins.

Fortunately research on the PSF is largely funded privately by the Gordon and Betty Moore Foundation.
While universities like Harvard have had their funding cut by Trump, Australian universities have been also been threatened having to conform to the requirements of an idiotic questionnaire which includes the following questions.

Does your organization encourage free speech and encourage open debate and free sharing of information?
Can you confirm that your organization does not work with entities associated with communist, socialist, or totalitarian parties, or any party that espouses anti-American beliefs?
Can you confirm that your organization has not received ANY funding from the PRC (including Confucius Institutes and/or partnered with Chinese state or non-state actors), Russia, Cuba, or Iran?
Can you confirm this is not a climate or "environmental justice" project or include such elements?
Does this project directly contribute to limiting illegal immigration or strengthening US border security?
Does this project take appropriate measures to protect women and to defend against gender ideology…………?

As a response to nonsense like this, Australian scientists and academics have been advised when travelling to the States to use Burner phones after a French scientist was deported for having messages on his phone which were critical of Trump.
U.S. Customs and Border Protection (CBP) officers have been empowered to conduct frequent and invasive searches of travelers' electronic devices without warrants. These searches can include accessing emails, messages, social media accounts, and other personal data. Refusing to unlock a device can lead to detention, denial of entry, or seizure of the device.

 

[Hans Blaster]

The correct terminology is the Commander in Chief of the Grand Assembly of Imbeciles as highlighted in another thread with tariffs imposed on the activities of penguins.

C-in-C only applies to command of uniformed military personnel and their civilian commanders. For regular executive activity the correct term is "Chief Exectutive Imbecile". "The Grand Assembly of Imbeciles" is a separate branch of government.

 

[AV1611VET]

C-in-C only applies to command of uniformed military personnel and their civilian commanders. For regular executive activity the correct term is "Chief Exectutive Imbecile". "The Grand Assembly of Imbeciles" is a separate branch of government.

I'd rather be called that, than "The Father of Evolution."

 

[sjastro]

C-in-C only applies to command of uniformed military personnel and their civilian commanders. For regular executive activity the correct term is "Chief Exectutive Imbecile". "The Grand Assembly of Imbeciles" is a separate branch of government.

I've never been a fan of AI art as I find it too psychotic in the mould of a Hieronymus Bosch or Francesco Goya but it has nailed it here.
Looks as if according to your flag quite a few States were smart enough to secede.

 

[AV1611VET]

Looks as if according to your flag quite a few States were smart enough to secede.

And they seceded to protect their interests in the slave market.

As I'm fond of pointing out:

The Civil War

The South was pro slavery.​

The North was anti slavery.​

And God broke the tie.​

 

[juvenissun]

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.

Scientists have hypothesized the existence of exoplanets called hycean worlds - covered by a liquid water ocean habitable by microorganisms and with a hydrogen-rich atmosphere.

Earlier observations by Webb, which was launched in 2021 and became operational in 2022, had identified methane and carbon dioxide in K2-18 b's atmosphere, the first time that carbon-based molecules were discovered in the atmosphere of an exoplanet in a star's habitable zone.

DMS and DMDS, both from the same chemical family, have been predicted as important exoplanet biosignatures. Webb found that one or the other, or possibly both, were present in the planet's atmosphere at a 99.7% confidence level, meaning there is still a 0.3% chance of the observation being a statistical fluke.
The gases were detected at atmospheric concentrations of more than 10 parts per million by volume.

"For reference, this is thousands of times higher than their concentrations in the Earth's atmosphere, and cannot be explained without biological activity based on existing knowledge," Madhusudhan said.

How do we know the organic gases are the products of synthesis or decomposition? If they are products of decomposition, then they would only go down the drain further in the future.