Feinstein, Adina DAdina DFeinsteinRadica, MichaelMichaelRadicaWelbanks, LuisLuisWelbanksMurray, Catriona AnneCatriona AnneMurrayOhno, KazumasaKazumasaOhnoCoulombe, Louis-PhilippeLouis-PhilippeCoulombeEspinoza, NéstorNéstorEspinozaBean, Jacob LJacob LBeanTeske, Johanna KJohanna KTeskeBenneke, BjörnBjörnBennekeLine, Michael RMichael RLineRustamkulov, ZafarZafarRustamkulovSaba, AriannaAriannaSabaTsiaras, AngelosAngelosTsiarasBarstow, Joanna KJoanna KBarstowFortney, Jonathan JJonathan JFortneyGao, PeterPeterGaoKnutson, Heather AHeather AKnutsonMacDonald, Ryan JRyan JMacDonaldMikal-Evans, ThomasThomasMikal-EvansRackham, Benjamin VBenjamin VRackhamTaylor, JakeJakeTaylorParmentier, VivienVivienParmentierBatalha, Natalie MNatalie MBatalhaBerta-Thompson, Zachory KZachory KBerta-ThompsonCarter, Aarynn LAarynn LCarterChangeat, QuentinQuentinChangeatDos Santos, Leonardo ALeonardo ADos SantosGibson, Neale PNeale PGibsonGoyal, Jayesh MJayesh MGoyalKreidberg, LauraLauraKreidbergLópez-Morales, MercedesMercedesLópez-MoralesLothringer, Joshua DJoshua DLothringerMiguel, YamilaYamilaMiguelMolaverdikhani, KaranKaranMolaverdikhaniMoran, Sarah ESarah EMoranMorello, GiuseppeGiuseppeMorelloMukherjee, SagnickSagnickMukherjeeSing, David KDavid KSingStevenson, Kevin BKevin BStevensonWakeford, Hannah RHannah RWakefordAhrer, Eva-MariaEva-MariaAhrerAlam, Munazza KMunazza KAlamAlderson, LiliLiliAldersonAllen, Natalie HNatalie HAllenBatalha, Natasha ENatasha EBatalhaBell, Taylor JTaylor JBellBlecic, JasminaJasminaBlecicBrande, JonathanJonathanBrandeCaceres, ClaudioClaudioCaceresCasewell, S LS LCasewellChubb, Katy LKaty LChubbCrossfield, Ian J MIan J MCrossfieldCrouzet, NicolasNicolasCrouzetCubillos, Patricio EPatricio ECubillosDecin, LeenLeenDecinDésert, Jean-MichelJean-MichelDésertHarrington, JosephJosephHarringtonHeng, KevinKevinHengHenning, ThomasThomasHenningIro, NicolasNicolasIroKempton, Eliza M-REliza M-RKemptonKendrew, SarahSarahKendrewKirk, JamesJamesKirkKrick, JessicaJessicaKrickLagage, Pierre-OlivierPierre-OlivierLagageLendl, MonikaMonikaLendlMancini, LuigiLuigiManciniMansfield, MeganMeganMansfieldMay, E ME MMayMayne, N JN JMayneNikolov, Nikolay KNikolay KNikolovPalle, EnricEnricPallede la Roche, Dominique J M Petit DitDominique J M Petit Ditde la RochePiaulet, CarolineCarolinePiauletPowell, DianaDianaPowellRedfield, SethSethRedfieldRogers, Laura KLaura KRogersRoman, Michael TMichael TRomanRoy, Pierre-AlexisPierre-AlexisRoyNixon, Matthew CMatthew CNixonSchlawin, EverettEverettSchlawinTan, XianyuXianyuTanTremblin, PPTremblinTurner, Jake DJake DTurnerVenot, OliviaOliviaVenotWaalkes, William CWilliam CWaalkesWheatley, Peter JPeter JWheatleyZhang, XiXiZhang2024-10-152024-10-152023-02https://boris-portal.unibe.ch/handle/20.500.12422/120321The Saturn-mass exoplanet WASP-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy1-4. However, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality5-9. Here, we present the transmission spectrum of WASP-39 b obtained using the SOSS mode of the NIRISS instrument on JWST. This spectrum spans 0.6-2.8𝝻m in wavelength and reveals multiple water absorption bands, the potassium resonance doublet, and signatures of clouds. The precision and broad wavelength coverage of NIRISS-SOSS allows us to break model degeneracies between cloud properties and the atmospheric composition of WASP-39b, favouring a heavy element enhancement ("metallicity") of ~10-30x the solar value, a sub-solar carbon-to-oxygen (C/O) ratio, and a solar-to-super-solar potassium-to-oxygen (K/O) ratio. The observations are also best explained by wavelength-dependent, non-gray clouds with inhomogeneous coverage of the planet's terminator.en500 - Science::570 - Life sciences; biology600 - Technology::610 - Medicine & healtharticle10.48350/1771343662355010.1038/s41586-022-05674-1