[HN Gopher] Webb Discovers Methane, Carbon Dioxide in Atmosphere...
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Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B
Author : wfurney
Score : 166 points
Date : 2023-09-11 15:04 UTC (6 hours ago)
(HTM) web link (www.nasa.gov)
(TXT) w3m dump (www.nasa.gov)
| fritzo wrote:
| 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.
| V1ndaar wrote:
| 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...
| sgt101 wrote:
| 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 wrote:
| > Complex animal life took 3.5 bn years to emerge on Earth,
|
| How certain are we it took that long (the first time)?
| tracedddd wrote:
| Not certain at all, it's based on last universal common
| ancestor estimates(LUCA) and supported by (lack of) fossil
| record.
| wolverine876 wrote:
| > it's based on last universal common ancestor
| estimates(LUCA) and supported by (lack of) fossil record.
|
| I thought the Cambrian Explosion's fossil record was pretty
| sizeable - in fact, it's named after the place where the
| fossil layer was first discovered. I didn't know it was
| related to a common ancestor. Are you thinking of something
| else or am I missing something major?
| edgyquant wrote:
| Yes but we're talking about before the Cambrian
| no_wizard wrote:
| Its _possible_ there is a good explanation for why there
| would be no strong fossil record[0] for an advanced
| civilization preceding us.
|
| >When it comes to direct evidence of an industrial
| civilization--things like cities, factories, and roads--the
| geologic record doesn't go back past what's called the
| Quaternary period 2.6 million years ago. For example, the
| oldest large-scale stretch of ancient surface lies in the
| Negev Desert. It's "just" 1.8 million years old--older
| surfaces are mostly visible in cross section via something
| like a cliff face or rock cuts.
|
| While I think its highly unlikely (I mean less than
| 0.00001% possible) the means in which we would could even
| detect it are complicated
|
| [0]:
| https://www.theatlantic.com/science/archive/2018/04/are-
| we-e...
| delta_p_delta_x wrote:
| 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.
| no_wizard wrote:
| When you say very little, do you mean none, or there is
| some questionable evidence?
|
| I'm genuinely curious
| dudinax wrote:
| Before "modern" life evolved in the pre-cambrian era,
| there was the Ediacaran life forms that were complex
| multicellular life, but died out millions of years before
| the Cambrian explosion.
|
| https://en.wikipedia.org/wiki/Ediacaran_biota
| TheBlight wrote:
| Given the surface of the planet is such a dynamic
| environment, I wonder how much evidence we should expect
| even if it did exist.
|
| See also: https://www.scientificamerican.com/article/could-
| an-industri...
| Rebelgecko wrote:
| There's quite a few fossils showing single-celled
| organisms from 3+ billion years ago. I imagine if more
| complex life existed the fossils could've survived
| svachalek wrote:
| 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.
| skywal_l wrote:
| Seems to be down. This page seems to work:
| https://webbtelescope.org/contents/news-releases/2023/news-2...
| bayesianbot wrote:
| 404 not found, did they maybe remove the article for some reason?
| [deleted]
| biggestlou wrote:
| I'm still looking for intelligent life on _this_ planet
| [deleted]
| nickhalfasleep wrote:
| 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 wrote:
| 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!
| jncfhnb wrote:
| Suppose a planet like this had non intelligent megafauna life.
| How could we detect this?
| dudinax wrote:
| One way is to build bigger telescopes and hope its not too
| cloudy.
| floxy wrote:
| "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
| CodeL wrote:
| [flagged]
| perihelions wrote:
| 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.
| Jeff_Brown wrote:
| In case you wondered too, this is 124 light-years from us.
| Aachen wrote:
| 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 wrote:
| 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.
| coffeebeqn wrote:
| How do you get the rover there? It would take thousands of
| years. Or maybe millions of years? With the current tech
| NoMoreNicksLeft wrote:
| 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.
| floxy wrote:
| "Roundtrip Interstellar Travel Using Laser-Pushed
| Lightsails"
|
| https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1
| .10...
| jandrese wrote:
| Even worse if we are still limited by Newtonian dynamics it
| will take thousands of years for a probe to reach there.
| The rocket equation is a harsh mistress. In practical terms
| we will never visit that world without completely upending
| physics as we know it.
| holoduke wrote:
| We just need a 1g rocket. Will take only a few days to
| get there. Life on earth will be 1000 years ahead once we
| are back though.
| jandrese wrote:
| The problem is when you work out the math on rocket that
| can sustain 1G for multiple days with any Earthly isp you
| realize the math just doesn't work. Even if you go nuts
| and plug in a number like 1 million seconds (our best
| chemical rockets are more like 450 seconds) for the isp
| it is still nowhere close to feasible using only the mass
| of our solar system.
|
| As long as you are stuck flinging mass out of the back of
| your rocket to accelerate you don't get to go anywhere
| outside of our solar system.
| polishdude20 wrote:
| 2185? Not 2273?
| hungryforcodes wrote:
| 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.
| wfurney wrote:
| https://web.archive.org/web/20230911143418/https://www.nasa....
| v8xi wrote:
| 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.
| behnamoh wrote:
| 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.
| alexpotato wrote:
| 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
| joshlemer wrote:
| 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.
| [deleted]
| fmobus wrote:
| I think 8g would be pretty hard to escape from, at least with
| chemical rockets.
| ericbarrett wrote:
| 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 exactly 1 Earth g on the
| surface. This implies it's over 10x as dense.
| wheels wrote:
| Gravity is only about 1.25 g, according to Wikipedia. Density
| matters. The earth and Saturn have about the same surface
| gravity.
| [deleted]
| lovecg wrote:
| 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.
| watersb wrote:
| 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.
| littlestymaar wrote:
| 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.
| jdblair wrote:
| 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
| everyone wrote:
| Thanks for that! I need a new novel to read, just
| downloaded it!
| colechristensen wrote:
| 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.
| 0xfaded wrote:
| Assuming roughly comparable density to earth, the surface
| gravity would only be 2g
| thelittleone wrote:
| Perhaps they're gas like.
| gizmo686 wrote:
| Gravity is more relevant for land based life. However, we
| know from Earth that complex life can evolve in oceans.
| pdonis wrote:
| 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.
| adolph wrote:
| That is if density remains constant. If the planet were 8x
| mass but with same radius, gravity would be 8 g, or 8 x
| 9.795 m/s^s. Earth mass: 5.97x10^24
| kg, 6378.137 km yields 9.795 m/s^2 8x mass:
| (8x5.97)x10^24 kg, 6378.137 km yields 78.36 m/s^2
|
| All calculations: https://www.wolframalpha.com/input?i=surf
| ace+gravity+calcula...
| pdonis wrote:
| _> That is if density remains constant._
|
| No, the calculation I made did not assume constant
| density. I just used the direct Newtonian formula for
| surface gravity and plugged in the known mass and radius
| of the planet. (You could also use that known mass and
| radius to calculate the average density. But you don't
| need to do that to calculate the surface gravity.)
|
| _> If the planet were 8x mass but with same radius_
|
| But we know it isn't. We know the planet's radius is 2.6
| times the Earth's radius. That's stated in the article.
| dylan604 wrote:
| 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.
| julienchastang wrote:
| Thanks for the book recommendation. Added to reading list.
| lofaszvanitt wrote:
| 120 light years away. Time to get the ufo tech out already.
| 7373737373 wrote:
| 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_wizard wrote:
| 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.
| coldpie wrote:
| 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...
| svachalek wrote:
| 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.
| lofaszvanitt wrote:
| The ufos have to come from somewhere, right?
| coldpie wrote:
| Yeah, flawed lenses and windows, and unreliable witnesses.
| No need for FTL there.
| NoMoreNicksLeft wrote:
| 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.
| ZunarJ5 wrote:
| This feels like a big deal. The website seems to be getting
| hammered as it is working on and off.
| willis936 wrote:
| 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 wrote:
| 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
| ZunarJ5 wrote:
| Yes, this is it!
| JackFr wrote:
| After getting sucked in by the phosphine on Venus hype, I
| refuse to get hurt again. . .
| [deleted]
| swader999 wrote:
| Nice to know we aren't the only ones struggling with CO2.
| julienchastang wrote:
| 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-...
| kaycebasques wrote:
| 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.
| julienchastang wrote:
| From a single pixel of light! Indeed mind blowing.
| treyd wrote:
| 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.
| dghughes wrote:
| 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.
| finite_depth wrote:
| 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).
| cout wrote:
| > 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?
| marcosdumay wrote:
| I don't think anybody knows enough to tell you what kinds of
| reactions happen on planet-wide environments without an
| oxidizing atmosphere.
| divbzero wrote:
| > "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_massa wrote:
| 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.
| nofitty376 wrote:
| 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...
| fritzo wrote:
| Right, show a posterior distribution not some hallucinated
| point estimate.
| V1ndaar wrote:
| Check out the paper and not a PR piece [0].
|
| [0]: https://stsci-
| opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf
| bigbillheck wrote:
| > 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_massa wrote:
| 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).
| gus_massa wrote:
| [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
| absorcion 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.)
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(page generated 2023-09-11 22:01 UTC)