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

nasa.gov

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

#111

Post by fbdab103 »

svachalek wrote: post #69
sgt101 wrote: post #2

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.

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 happ…

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.

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

#112

Post by rayrey »

thot_experiment wrote: post #110
pdonis wrote: post #53

Earlier quoted context omitted.

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.

Juuuuusssttt barely below the limit to be able to launch chemical rockets into space (IIRC it's ~1.3g)

Lol.

Seeing that response and then your username

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

#113

Post by thenickdude »

nextaccountic wrote: post #109
bigbillheck wrote: post #73

Earlier quoted context omitted.

> 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, wher…

what means planet's terminator?

The boundary between daytime and nighttime [0]

[0]: https://en.wikipedia.org/wiki/Terminator_(solar)

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

#114

Post by ethbr1 »

ericbarrett wrote: post #83
fmobus wrote: post #47

Earlier quoted context omitted.

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

Earth's surface gravity is really on the edge of what's feasible for chemical rockets; IIRC the limit is around 1.4g. Though as other commenters have mentioned, it's possible to have a much more massive planet that's also got a larger radius and thus has comparable surface gravity. Some fun trivia—the planet Kerbin from Kerbal Space Program is the opposite case. It has a radius of 600km, versus Earth's 6378km, but is…

To expand, isn't that limit "the most efficient possible chemical rockets, launched from sea level"?

I.e. air-breathing aircraft + chemical rockets would work, as would other exotic solutions

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

#115

Post by billforsternz »

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?

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

#116

Post by NoMoreNicksLeft »

floxy wrote: post #91
NoMoreNicksLeft wrote: post #80

Earlier quoted context omitted.

Orion drives can get up to some respectable fraction of the speed of light. Just need a billion or so 1-kiloton nukes. No biggy. No worries about sneaking up on them and startling them either.

"Roundtrip Interstellar Travel Using Laser-Pushed Lightsails" https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.10...

Ok, but let's bring along some nukes anyway, just for giggles.

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

#117

Post by kjkjadksj »

perihelions wrote: post #82

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/STSc…

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.

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

#118

Post by kjkjadksj »

fbdab103 wrote: post #111
svachalek wrote: post #69

Earlier quoted context omitted.

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 happ…

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 org…

It not only has to work, the mutant has to have a fitness advantage over the nonmutant or it will drop out of the population before long. The vast majority of mutations are also “bad.”

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

#119

Post by truculent »

billforsternz wrote: post #115

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-s…

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

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

#120

Post by kjkjadksj »

treyd wrote: post #57
julienchastang wrote: post #13

Earlier quoted context omitted.

From a single pixel of light! Indeed mind blowing.

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 no…

If you were at such distance from the earth, what would be resolvable?
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