Did JWST find a MARKER OF LIFE in an exoplanet atmosphere?

the James of Space Telescope has been hit in the headlines again this week for both the right and the wrong reasons after this paper describing observations of the exoplanet k218b was published by Medusa dining collaborators for the right reasons because this work is really exciting because it helps to solve what's known as the missing methane problem in exoplanet studies and also classify k218b as a Haitian world so a planet with an ocean surrounded by a hydrogen atmosphere hence but for the wrong reasons because a lot of media Outlets jumped on this claim of a detection of dimethyl sulfide which is a bio signature a marker for Life supposedly in the atmosphere of k218b but that the paper doesn't actually present strong enough evidence for and there's lots of caveats for the weak evidence they do have so let's dive into this this week we're going to chat about first what we already know about the planet k218b to how jwst studies exoplanets using what's known as a transit three what Medusa down and collaborators have found and why it's exciting for the caveats to these results especially that biomarker claim of dimethyl sulfide and five what's next how do we confirm or deny this claim so let's start with k218b itself it's an exoplanet so a planet orbiting a red dwarf star 124 light years away from the sun in the direction of the constellation of Leo it obviously star at a distance of about 21 million kilometers that's about 16 of the distance from Earth to the sun taking just under 33 Earth days for a single orbit around so it's much closer to its star than Earth is to the Sun but red dwarfs are much smaller and cooler than the Sun so that means that k218b is still in what's known as the habitable zone where the amount of light received from a star means that the temperature of the planet at least depending on its atmosphere anyway would be in the right range to support life at least Life as we know it here on they actually received a very similar amount of light as the Earth does from the Sun so it's long been considered a potential candidate for a habitable world however it is not a rocky planet like Earth because it is 8.63 times heavier than the earth but has a radius of only 2.6 times wider meaning that it is much denser than Earth so it's actually classed as more of a mini Neptune now there's three ways that you could explain the size mass and density of k218b given the amount of light that it receives from its star and the temperature it most likely is either it is a literal mini Neptune gas planet with a deep and dense hydrogen atmosphere or it has a dense Rocky core just a bit bigger than Earth surrounded Again by a deep dense hydrogen atmosphere and by dense here I mean like a thousand times the pressure of Earth's atmosphere at sea level or three it is a Haitian world with a thinner hydrogen atmosphere over a dense water ocean hence hyphen it's a portmanteau of hydrogen and ocean which annoyingly I'm not sure how to pronounce I'm pronouncing it like high from hydrogen and shin from Ocean so hyphen but like as it's written in English you would probably pronounce it as like hycian pretty sure it's Hai Shin but let me know how you pronounce it down in the comments now thankfully we should be able to tell these three scenarios apart with the right data so who in collaborators in 2021 pointed out the different mix of molecules that you get with a hyphen World versus a thick hydrogen atmosphere over a rocky or a gas core so that's what we need to find out what is the atmosphere of k218b made of and so how do we do that with jwst when we wait until the planet on its orbit passes in front of its star from our perspective here on Earth what's known as a planet Transit and we compare the light we receive before the transit and during the transit of the planet that way we can remove what the Starlight looks like and we just get left with what happens to the light as it passes through the atmosphere of the planet where the different molecules will steal away different wavelengths or colors of light so that we see see these as drops in the amount of light we receive sometimes you might also see this plotted as the amount of light blocked so essentially it's just this graph but upside down and we'll get bumps up at certain wavelengths where there's more light been absorbed so this kind of observation has been done before for k218b but using the hobble Space Telescope which detects light in the optical and then just into the near infrared parts of the spectrum and in 2019 Beneke and collaborators reported the detection of water vapor in the atmosphere of k218b again this plot shows the amount of light absorbed at the different wavelengths so any bumps upward is the presence of a molecule in this case water which Drew even more attention to k218b at the time because not only was it a planet in its habitable zone around its star but it also had water vapor in its atmosphere as well but these observations with the Hubble Space Telescope couldn't tell us whether or not this was a Haitian world because the molecules that Hue and carburetors had highlighted as being the ones you need to look for like methane and carbon dioxide to work out whether it's a Haitian world or not those molecules absorb in the infrared part of the spectrum and not the optical where the Hubble Space Telescope looks which is why you need jwst so this is exactly what Medusa down and collaborators applied to do with jwst so what did they find well they observed two transits of k218b the first in January 2023 with an instrument called near spec and the second in June 2023 at slightly shorter wavelengths with an instrument called nearest onboard jwst nearest has some slight overlap into the near infrared with the Hubble Space Telescope as well which meant that they could compare their observations there with the previous observations and so here is what that data looks like again we've got the amount of light absorbed along the y-axis here so any bumps upwards are from molecules absorbing light in the atmosphere of k218b if I just add the Hubble Space Telescope data in here as well in the black you can just compare how much of a larger wavelength range jwst actually covers so what you're seeing here first of all the orange points and then the error bars around them are the nearest data the shorter wavelengths then you've got the red points in the error bars Associated at the longer wavelengths taken with the neospec instrument the dark blue line is a much more detailed model spectrum of what the planet would look like with the light blue shading just the uncertainty on the model then the yellow points are the values of that model but at the resolution of the data so for every observational data point in either the orange or the red there's a yellow model point to match which if the model is a good fit should be a very close match to the data points at least within the uncertainties on the data and all of these bumps in the amount of light absorbed are caused by a mix of various different molecules right and a best fit has to work out whether the molecule is present and in what concentration to give you the right sized bump in the model that you're fitting to your data now that's easier to do for some molecule now that's easier to do for some molecules than it is for others like for example methane CH4 where it absorbs light in regions where no other molecules tend to absorb so if you see a bump there you know that it can only have been created by methane but it's much harder for other molecules like for example dimethyl sulfide because it absorbs light where other molecules also absorb light so if you see a bump there it could be caused by methane or dimethyl sulfide or something else entirely so we say that dimethyl sulfite is Degen generate with methane essentially you could confuse it for methane and if you have a best fit model it's got to take that into account with all of the uncertainties that come with that so here's those uncertainties sort of represented with these histogram for their best fit model just focus on the the blue histograms here and you'll see that the best bit model gives a 0.9 concentration of methane and a 1.7 concentration of carbon dioxide a mix of molecules which confirmed k218b as a Haitian World a planet with a liquid water ocean surrounded by a thin hydrogen-dominated atmosphere but you'll also see that Medusa down and carburetors claimed a 0.3 concentration of dimethyl sulfide the molecule that everybody got excited about because here on Earth the main producer of dimethyl sulfide is phytoplankton in the ocean hence why it's considered a bio signature or a marker for life now we also technically make it in industrial processes it's a byproduct of making wood pulp to make paper but there's no known sort of like volcanic or geological process that makes dimethyl sulfide there's no known chemistry in the atmosphere that can make it either but that's not to say that on any other planet there might be some chemistry that is yet unknown to us that can actually make dimethyl sulfide it's a very similar situation to what we were in when we found phosphine in the atmosphere of Venus another molecule that's only produced by life and Industry here on Earth but let's face it in Venus's atmosphere which is incredibly inhospitable is most likely to be coming from some unknown chemistry in the atmosphere with k218b given sort of all of the hype around jwst you know searching for these biosignatures in you know habitable worlds everyone was always sort of Twitchy for the first one that we were going to find but if we actually look at the statistics here that medusudan have found in their model there's actually a one in 66 chance that the detection of dimethyl sulfide is just a statistical fluke caused by noise in the data whereas the methane detection they have has a one in two million chance of being a fluke so while the claim for the detection of methane is really strong the claim for the detection of dimethyl sulfide really isn't it isn't even over the statistical thresholds that we usually use to actually claim a detection so from that alone I don't think we can even claim that we've detected dimethyl sulfide in the atmosphere of k218b that's not to say that these results aren't still exciting because the really strong claim for the detection of methane not only confirmed that this was a hyphen world but also helped to solve the missing methane problem along with another research study that was released this past we week by Bell and collaborators which got way less pressed than this one but who also found methane in very strong concentrations in the atmosphere of the exoplanet wasp 80b putting to rest over a decade's worth of confusion over why we weren't detecting methane in exoplanet atmospheres given how prolific it is in our own solar system and yet all the media coverage has been about dimethyl sulfide because everybody wants to find a biosignature despite the fact that we really don't have strong enough evidence to claim that yet as we just heard not only that but there's a huge number of caveats to these results as well first of all that Medusa Nano carburetors only used one method of taking the raw data and extracting this absorption spectra that was their final result what's called a data pipeline a pipeline because you know you put raw data in from the telescope and out pops a nicely reduced data that you can plot as your absorption spectrum and it takes into account all the sources of noise and maybe the fact that there's some star spots that have been affecting the transit as well but there's many different ways that you can account for all of that stuff so there's now a lot of different jwst EXO Planet data reduction pipelines that exist out in the world and a research study looked into this earlier this year and they found that these different pipelines actually end up affecting the results and the concentrations of the different molecules that you can actually claim and that paper was written by constantinu Gandhi and Medusa down the first author of the k218b study so the fact that they only used one pipeline in the k218b study is a little bit frustrating because it makes you wonder whether the results might have changed if another pipeline was used now ideally what you would have is another independent research group also analyzed this data Maybe running through different pipelines and check the results but we're not going to have that for another couple of months yet because jwst data doesn't get made public until 12 months after it was taken so for the near spec data that's going to be in January 2024 and the nearest data that's going to be June 2024. so by the time that people get their hands on that data running through the pipelines analyze it publish their work it's going to be a way off yet but the good news is we do have a plan for going forward because more observations of k218b are already planned for this cycle of jwst observations thanks to this proposal from Hugh and Damiano that plans to observe k218b again with Nia spec and this proposal again led by Medusa down that plans to observe k218b with Miri the Miri data is especially going to help here because the Miri instrument on board jbst looks at much longer wavelengths than either near spec or nearest and dimethyl sulfide absorbs much more strongly at those longer wavelengths around about seven microns or so and it is not degenerate with anything else like for example methane like it is at these lower wavelengths where you can't pick out which one is actually doing the absorption so we should know in the next year or two whether that actually is dimethyl sulfide in the atmosphere of k218b or not and if we can actually claim to have detected a bio signature with Jade West t a big thanks for this episode go to my colleagues Dr Jake Taylor Professor Jane Burke B and Dr Ryan McDonald who are all fantastic exoplanet experts and gave me some insight into how this research had been received in their field if you want to give them a follow I'll link their social media Pages below for now though like until we have any new generosity observations of k218b or until anybody re-analyzes the current data we have for k218b I think we need to take this claim over detection of dimethyl sulfide in its atmosphere and then of course the very large jump from the presence of dimethyl sulfide to life on that planet with a very healthy dose of scientific skepticism what is going on outside there's like work being done on the road it sounds like it's almost like an angle grinder to the road so it's really noisy Lorry but do that again what is that holy I have no idea what the name of those things are but it was kind of like a little digger like you know with like little tank wheels and then like a giant Pokey stick on the end presumably for like drill it into the tarmac it was just rolling along it wasn't even Drilling and it was making so much noise the main producer of dimethyl sulfide is photoplankton in the ocean phytoplankton not photoplankton look in physics if it's a pH at the start of a word it's most likely the the prefix is going to be photo but this in this case it's phytopointing I was like oh photoplankton do they glow no what's called a data with a very very large dose dose a very large dose of healthiest

Channel: Dr. Becky

Views: 282,204

Keywords: dr becky, astrophysics, physics, space, universe, scientist, solar system, astronomer, telescopes, james webb space telescope, aliens, NASA, ESA, becky smethurst, infrared, MIRI, NIRCam, unfoldtheuniverse, cosmos, redshift, technology, exoplanets, JWST, exo-earth, earth-like planets, alien life, search for life, atmospheres, water, carbon dioxide, photochemistry, spectroscopy, absorption, biosignature, methane, phosphine, chemistry, hubble, NIRSPEC, NIRISS, exoplanet, carl sagan, dimethyl sulfide, DMS, K2-18b, life

Id: F360SGAlI8Y

Length: 17min 4sec (1024 seconds)

Published: Thu Sep 21 2023