Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b/

by wfurney • 3 years ago

235 135 3 years ago

sgt1012• 3 years ago

Gosh - imagine that place!

I wonder how old this world is, and how stable its enviroment is/has been. Complex animal life took 3.5 bn years to emerge on Earth, of course that's a meaningless data point by itself but intuitively for this place to have an ecosystem or complex life it needs to be old.

Still, even without this what a wonderful and weird environment.

unsupp0rted• 3 years ago

Complex animal life took 3.5 bn years to emerge on Earth,

How certain are we it took that long (the first time)?

tracedddd• 3 years ago

Not certain at all, it’s based on last universal common ancestor estimates(LUCA) and supported by (lack of) fossil record.

delta_p_delta_x• 3 years ago

The fossil record. There is little evidence of very complex animal life before about 541 million years ago, which is when the Cambrian explosion begun.

svachalek2• 3 years ago

Single cell life appeared on Earth almost instantly after the planet cooled down enough to allow it. I don't think it's clear that any progress was being made over the next few billion years. One day the right mutation happened and boom, fancy life everywhere. With our data sample of one, I don't think it's clear if it was extraordinarily bad luck it took that long to happen, or extraordinarily good luck it ever happened at all.

fbdab103• 3 years ago

Eukaryotic cell is such a bonkers insane development, I definitely lean towards the impossibly lucky scenario. There was no need for that to be the origin story of a mitochondria like organelle (https://en.wikipedia.org/wiki/Symbiogenesis), but that's what we think we have.

That being said, there was an experiment (https://www.pnas.org/doi/full/10.1073/pnas.1115323109) which was able to select single cellular organisms to "become multicellular" in a rapid amount of time (<50 generations? been a while since I read it). Which says to me that, theoretically, the process is not hard, it just requires trillions of attemps to evoke something that works.

skywal_l• 3 years ago

Seems to be down. This page seems to work: https://webbtelescope.org/contents/news-releases/2023/news-2...

bayesianbot• 3 years ago

404 not found, did they maybe remove the article for some reason?

wfurney• 3 years ago

https://web.archive.org/web/20230911143418/https://www.nasa....

ZunarJ52• 3 years ago

This feels like a big deal. The website seems to be getting hammered as it is working on and off.

willis936• 3 years ago

What makes it feel like a big deal? Carbon, oxygen, and hydrogen are extremely abundant. Those molecules are relatively low energy combinations of the elements. I would be surprised to not find them in the atmospheres of big rocky planets.

bilekas• 3 years ago

Apperantly it seems to be the presence of " dimethyl sulfide ". It seemingly only produced, on earth at least, by life. So using us as a baseline it seems pretty interesting.

DMS is generated by the degradation of dimethylsulfoniopropionate, which is present in many species of marine algae and plants, including dinoflagellates and coccolithophores

kaycebasques• 3 years ago

It's mind-bendingly cool that people can figure out the composition of an atmosphere without actually being close to that atmosphere.

Had not heard of dimethyl sulfide before. That's a good keyword to know.

julienchastang3• 3 years ago

From a single pixel of light! Indeed mind blowing.

treyd• 3 years ago

That's somewhat misleading though. It's not really a pixel in that there's much more information available than, basically, 3 integers between 0 and 255. There's 4 instruments on the telescope that collect 4 different chunks of IR spectra, and there's very precise and granular intensity values for light received around any given wavelength. Much more detail than a "pixel" has in the typical sense we use them.

It's not a lot of information, not nearly enough to identify surface features on an exoplanet, but it's very useful data if you're trying to identify likely chemical composition of bodies or how hot clouds of gas are.

finite_depth• 3 years ago

This is an easier problem than it probably seems. Atmospheres are relatively low-density gas, which means they produce an absorption spectrum - a chemical fingerprint that identifies most atoms and molecules quite reliably. It's such a good fingerprint that it was used to discover several chemical elements, most notably helium (observed in the Sun's spectrum before it was known on Earth).

dghughes• 3 years ago

For emission spectroscopy has been a thing since 1859 when Gustav Kirchhoff figured it out but for stellar emission spectroscopy it was Joseph von Fraunhofer in early 1800s? Although 1866, Pietro Angelo Secchi may have also discovered stellar emission spectroscopy 1848.

An amazingly long time ago.

cout• 3 years ago

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.

Given a sufficient quantity of reactants/reagents, could DMS be produced via a natural process, or is this a sufficiently unfavorable reaction that it's unlikely?

marcosdumay2• 3 years ago

I don't think anybody knows enough to tell you what kinds of reactions happen on planet-wide environments without an oxidizing atmosphere.

kjkjadksj6• 3 years ago

Chemist certainly do. Reactions are carried out at specific atmospheric conditions. E.g. oxygen may well be purged.

kjkjadksj6• 3 years ago

It is produced industrially without needing life. I’m not sure why its the alleged smoking gun if theoretically if the conditions are right and the reaction is catalyzed it will go on without needing a lifeform.

2 CH3OH + H2S → (CH3)2S + 2 H2O

v8xi• 3 years ago

In Nick Lane's Oxygen: The Molecule that Made the World, he talks about the importance of both methane and carbon dioxide and how they exist at the extremes of a complex metabolic oxidation-reduction cycle. Methane stores a lot of chemical energy in its C-H bonds which can be burned directly, or metabolized through repeat oxidation events to ultimately form CO2, which plants utilize with the help of the sun to form more CH bonds before ultimately breaking down into methane again. Hence, an exoplanet with both molecules in its atmosphere is a promising candidate in the search for life.

julienchastang3• 3 years ago

Thanks for the book recommendation. Added to reading list.

behnamoh• 3 years ago

I wonder what life looks like on a planet which is over 8 times more massive than the Earth. Do animals have spines at all on a planet with almost 8g gravity? Does life even get to evolve into complex systems like animals under this much gravity? How about plants? Do they grow up or spread out instead?

If one day we get a visitor from this planet, they'll jump on our planet the same way human astronauts jumped on the Moon.

dylan6042• 3 years ago

The gravity question is one I've pondered myself as a thought exercise. There's been discussions on how far up a plant can draw water as the defining limit to how tall a tree could grow. Some discussions as well on how tall an animal could grow based on how high blood could be pumped up. Which is a direction different from the structural support and sizes that I find interesting.

lovecg• 3 years ago

Note that 8 times more massive doesn’t mean it has 8 times surface g, unless it’s exactly the same radius as the Earth. If the planet is larger you’re further away from the center of gravity.

For example, the Earth is 10 times more massive than Mars, but only has 2.6 times surface g.

0xfaded• 3 years ago

Assuming roughly comparable density to earth, the surface gravity would only be 2g

gizmo686• 3 years ago

Gravity is more relevant for land based life. However, we know from Earth that complex life can evolve in oceans.

watersb• 3 years ago

I wonder how much of an outlier we may be, shuffling around on dry land, when most of the biosphere of our planet is in the ocean.

Higher gravity certainly means higher pressure gradient, more pressure per vertical meter of ocean. And high pressure affects protein structure.

It's life, but not as we know it.

thelittleone• 3 years ago

Perhaps they're gas like.

joshlemer• 3 years ago

It would be really cool to run an experiment like this. Have some population of rats living in a large enclosure that is held in a large centrifuge for decades and see how they evolve.

fmobus• 3 years ago

I think 8g would be pretty hard to escape from, at least with chemical rockets.

wheels2• 3 years ago

Gravity is only about 1.25 g, according to Wikipedia. Density matters. The earth and Saturn have about the same surface gravity.

jdblair• 3 years ago

The classic sci-fi "Mission of Gravity" explores what life would be like on a rapidly rotating planet where one experiences 3g at the equator and 700g at the poles.

https://en.wikipedia.org/wiki/Mission_of_Gravity

colechristensen• 3 years ago

As others have mentioned it wouldn't be 8 g. Life would be smaller. There would be speed differences. A lot of optimums and limits depend on how volume scales against area. Like the biggest terrestrial animals are limited a characteristic dimension (height or length) x being proportional to femur area x^2 being proportional to mass x^3. Mass grows proportional to x^3, femur strength (area) grows proportional to x^2, so you have a limit on how big a thing can be when you run out of available femur strength.

Higher gravity means this upper limit will be smaller. All sorts of similar scaling things will change optimum points for structural and energy reasons.

pdonis2• 3 years ago

The planet's surface gravity is not 8 g. Surface gravity goes like mass over radius squared, and the planet's radius is 2.6 times Earth's, so the surface gravity will be 8 / (2.6)^2, or only about 1.2 times that of Earth.

alexpotato• 3 years ago

The book Dragon's Egg has a species living on a neutron start with millions of G's

https://en.wikipedia.org/wiki/Dragon%27s_Egg

littlestymaar• 3 years ago

In addition to what others have said about the fact this planet doesn't have 8g at its surface, at 8g you could still have many lifeforms that exists on earth, but only the small ones. Gravity grows roughly as the cube of your size (because your volume does), but bones resistance only get n² (because it's the surface that counts), so the bone resistance / weight ratio is inversely proportional to your size.

BurningFrog• 3 years ago

The g force isn't that important for this.

Assuming life develops in an ocean, like we did, organisms in water are essentially weightless, regardless of the g force.

mulletboy• 3 years ago

Can anyone recommend a good book on exoplanets speculative biology, flora & fauna, etc?

julienchastang3• 3 years ago

On this topic, I just finished reading "A Very Short Introduction to Planetary Systems"[0] by Raymond T. Pierrehumbert. He devotes a good portion of the book to exoplanet atmospheres. It is one of the best science books I've read. Pierrehumbert really has a knack for explaining complex material clearly and concisely. I really recommend it.

[0] https://global.oup.com/academic/product/planetary-systems-a-...

nickhalfasleep• 3 years ago

Scientists using Webb may be able to present some surprisingly strong evidence that we are not the only life bearing planet in the galaxy.

jug• 3 years ago

Yeah, not sure about the sensitivity, if it's particularly good conditions here but at least this data set looks like it gives remarkably little room for false positives and quite highly detailed. I thought it would push JWST a bit harder but this looks promising. Even a novice can read out the evidence for various molecules in that graph? So, if only we'd find an exciting result soon!

Jeff_Brown2• 3 years ago

In case you wondered too, this is 124 light-years from us.

Aachen3• 3 years ago

Wow, that's really close so far as these things go. With the nearest star being 4ly, this can be reached with essentially the same tech level if we'd want to visit that with a rover or generational ship one day

BoiledCabbage• 3 years ago

What's also crazy is if we did send a rover over there to hunt for life, and they found it, we'd have to wait 125 years to hear the result.

We all sit around knowing to listen to the skies sometime in October of 2185 to hear if the rover found life within the first month of its landing.

If we ever send a team to live there, we'd hear broadcasts of their lives from 125 years prior. A real portal in time - so cool.

hungryforcodes• 3 years ago

We'd need some fast tech for sure. However, what is also interesting is that the light from it is only 124 years old. So the planet is still very similar today probably.

mcv• 3 years ago

this can be reached with essentially the same tech level

I'm not so sure about that. I mean, at the moment both are impossible, but it's much easier to imagine traveling 4ly than 124ly. 4ly can be reached in a single lifetime if you accelerate a shop to .9c, which is technically possible. 124ly is going to be a multigenerational undertaking no matter what. The 248y communication lag is also a much bigger obstacle than an 8y lag.

I think once you can travel 124ly, you can travel 1000+ ly. You need to be completely self-sufficient and you're going to lose contact with home anyway. If you send a robot, you're not going to hear from that robot again in centuries, if ever.

lofaszvanitt3• 3 years ago

120 light years away. Time to get the ufo tech out already.

7373737373• 3 years ago

Unfortunately humanity has not yet understood the potential that is out there, and is too busy fighting over the limited one here on Earth.

no_wizard3• 3 years ago

is Faster Than Light travel even possible? I'm asking in a serious way.

I have always read that its impossible, at least within our current knowledge.

the only semi-plausible theory I've ever heard is that Blackholes might one day yield some way of traveling quickly across the universe but nobody has shown anything substantiated around that or anything else.

svachalek2• 3 years ago

There's no realistically plausible solution I've ever heard of, that is, ones that don't require millions of years of setup and entire stars worth of energy production. But that's with our current understanding of physics. While our current models seem nearly perfect and therefore nearly complete, there was a time they thought that about Newtonian physics. Perhaps some detail we need to understand dark matter or dark energy could spring the whole field wide open again.

lofaszvanitt3• 3 years ago

The ufos have to come from somewhere, right?

coldpie2• 3 years ago

FTL travel being impossible is basically the one thing where I completely irrationally reject the science :) It's just too depressing for me to accept. There's gotta be a loophole. There's just gotta be...

NoMoreNicksLeft3• 3 years ago

It's quite simple really. All we need is fast-as-light technology.

If you get in a ship and travel to Alpha Centauri at the speed of light, the travel seems instantaneous to you. But the people you leave behind think you've been gone 8 years when you return.

So instead, I propose that when the ship launches, we also propel the rest of the universe in the opposite direction also at the speed of light. Then, when the astronaut is scheduled to return, we propel the entire universe at the speed of light back to its original location.

All of reality undergoes time dilation. And the trip is basically instantaneous for all involved†.

† Note: This form of FTL is mildly costly in regards to energy expenditure.

floxy3• 3 years ago

Not a lot of help for interstellar travel, but I believe that most of the mass in the visible universe is traveling away from us at faster than the speed of light.

https://arxiv.org/pdf/astro-ph/0011070v2.pdf

shepardrtc• 3 years ago

You can't go FTL through spacetime. But some math shows that it might be possible to warp spacetime around you and propel you to somewhere faster than it would take light going through spacetime.

swader999• 3 years ago

Nice to know we aren't the only ones struggling with CO2.

jncfhnb• 3 years ago

Suppose a planet like this had non intelligent megafauna life. How could we detect this?

dudinax2• 3 years ago

One way is to build bigger telescopes and hope its not too cloudy.

floxy3• 3 years ago

"Direct Imaging of an Exoplanet with a Solar Gravity Lens (1 Km Resolution)":

https://arxiv.org/abs/1802.08421

...and an excellent video on the topic:

https://www.youtube.com/watch?v=NQFqDKRAROI

nofitty376• 3 years ago

That spectrum is so noisy. How can they infer the blue fit from the (noisy) white points? The data look almost consistent with flat (no detection). And even if there is a detection, it looks like many other models could potentially fit the data...

fritzo2• 3 years ago

Right, show a posterior distribution not some hallucinated point estimate.

V1ndaar2• 3 years ago

Check out the paper and not a PR piece [0].

[0] https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf

gus_massa3• 3 years ago

[I'm not an expert is spectroscopy, but let me guess.]

The bump at 4.3um looks real, and it seams to be an standard absorción of CO2. https://www.quora.com/Does-CO2-absorb-all-infrared-frequenci...

The bump at 1.2, 1.4 and 2.4um looks real. I found this showing a peak for CH4 at 2.325um. http://www.astrochem.org/data/CH4H2O.php

[Sorry for the sources, but I'm not an expert is spectroscopy.]

My guess is that they assumed something like

a% * CH4 + b% * CO2 + c% * H2O + others

and get the best fit for a%, b%, c%, ... using the white points. Later, using these numbers they draw the blue line.

The peak for DMS is not clear for my untrained eye, so I can't guess what they did there. (Perhaps it's just the best fit.) It would be nice to see the a graph of the blue line they guessed with DMS and a superimposed red line with and atmosphere with an alternative atmosphere where the DMS is replaced with something uninteresting (N2? H2O? More CH4? I have no idea what is uninteresting here.)

bigbillheck• 3 years ago

How can they infer the blue fit from the (noisy) white points?

By having a detailed model, and modern probabilistic techniques:

The planet’s terminator is modelled as a plane-parallel atmosphere in hydrostatic equilibrium, with uniform chemical composition. The chemical abundances and pressure-temperature (P-T) profile are free parameters in the model. The retrieval framework follows a free chemistry approach, whereby the individual mixing ratio of each chemical species is a free parameter.... Our canonical model comprises of 22 free parameters overall: 11 corresponding to the individual mixing ra- tios of the above chemical species, 6 for the P-T profile, 4 for the clouds/hazes and 1 for the reference pressure Pref , defined as the pressure at a fixed planetary radius of 2.61 R⊕. The Bayesian inference and parameter estimation is conducted using the MultiNest nested sam- pling algorithm (Feroz et al. 2009) implemented through PyMultiNest.

(Sections 2.4 and 3.1 from https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf)

And even if there is a detection, it looks like many other models could potentially fit the data...

Name three.

gus_massa3• 3 years ago

Can I help the GP?

In the paper they analyze 3 models, "no offset", "offset" and "offsetx2". It's strange that they get better fit for CO2 and CH3 en the "offsetx2" model, but in that model the DMS disappears. So there it at least one model.

Also, they analyze common molecules like CO2, CH4, H2O, NH3 and biologically interesting molecules like CH3-S-CH3 (DMS), HCN, CH3-Cl. From the discussion in the paper it looks like the CH3- part is important, so I'd like to see a brute force search with everything that is in https://en.wikipedia.org/wiki/Atmosphere_of_Titan and has a methyl group, like CH3-CCH, CH3-CN. My Chemistry and Astronomy is no so good, so I'd like to add CH3-OH, CH3-NH2, CH3-SH, CH3-CHO and a few more from https://en.wikipedia.org/wiki/List_of_interstellar_and_circu... I removed the ones that are big or has too many oxygen (like CH3-COOH).

nextaccountic• 3 years ago

what means planet's terminator?

fritzo2• 3 years ago

Paywalled paper: https://www.nature.com/articles/s41550-019-0878-9

Preprint: https://arxiv.org/abs/1909.05218

Figure 2 pp. 14 of the preprint shows much more plausible error bounds on the curve fit. That press release "best fit" curve is merely an artist's conception.

V1ndaar2• 3 years ago

Nope, that is the old paper about Hubble measurements of the same planet.

The preprint of the Webb based paper is here [0] from here [1].

[0] https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf

[1] https://webbtelescope.org/contents/news-releases/2023/news-2...

divbzero• 3 years ago

"Our ultimate goal is the identification of life on a habitable exoplanet, which would transform our understanding of our place in the universe," concluded Madhusudhan.

What sort of observation or measurement would allow us to identify life on an exoplanet?

gus_massa3• 3 years ago

A lot of O2. As far as we know, the only source of a lot of O2 in the atmosphere are photosynthetic bacteria-like. So it will be a clear sign of life.

There are some more subtle cases, like the one discussed in this paper.

perihelions• 3 years ago

What an unintuitive and sketchy-looking Bayesian model. They only have 11 chemicals in the database they're matching that messy IR spectrum against: 6 reasonable ones, and 5 bullshit ones that are only there because theory papers suggested that they'd be biomarkers of alien life. And, fit to just those 11 chemicals, the best-fit includes one of the bullshit ones (dimethyl sulfide, (CH₃)₂S).

https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf

Is this approach, like, sane? I'm not a Bayesian statistics expert.

kjkjadksj6• 3 years ago

A true Bayesian I don’t think would use evidence for life on earth as the silver bullet for life elsewhere. They’d at least set up a model that considers all possible planets in the entire universe and test to see if these putative signatures even give you the power to identify earth as a life holding planet with confidence.

biggestlou• 3 years ago

I’m still looking for intelligent life on this planet

rbanffy• 3 years ago

Ugh. If my napkin math is right, it's about 2G's for the same density as Earth.

Very unpleasant planet.

billforsternz3• 3 years ago

I picked up a random book in the science section of the city library today and opening it to a random page I started reading about an exciting "goldilocks" exoplanet discovery from 2015. Apparently this was the first exo-planet which had a positive spectroscopic identification of water in the atmosphere. It was a rocky world, 2 billion years old, 8 times Earth's size (mass?), on a 33 day orbit around a red dwarf. K-something-or-other. The book said the really exciting discoveries will happen when Webb comes online in 2021. The link is down, but someone mentions this planet is 8 x Earth size down thread. I wonder if it's the same planet?

truculent• 3 years ago

I think this is supposedly a Hycean (ocean + hydrogen atmosphere) planet, rather than rocky. Unless those categories aren’t exclusive.

billforsternz3• 3 years ago

Sorry, didn't notice this in a timely way. I went back to the library to check, and indeed the planet I was reading about was K2-18b. The book at least says that K2-18b is a Super-Earth and will almost certainly have a molten rocky core.

stevenwoo• 3 years ago

Maybe you mixed up the dates slightly?

K2-18b (name of the exo-planet) orbiting star K2-18 was discovered in 2015 but the water was not detected until 2019.

billforsternz3• 3 years ago

Sorry, didn't notice the reply in a timely way. I went back to the library, the book was "The Universe" by Andrew Cohen. It was indeed K2-18B, discovered by Kepler in 2015. It says that the water was discovered by Hubble later, so presumably 2019.

Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

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