Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18 b

Tsiaras, Angelos; Waldmann, I. P.; Tinetti, Giovanna; Tennyson, Jonathan; Yurchenko, Sergei N.

doi:10.1038/s41550-019-0878-9

Cited by 294 publications

(282 citation statements)

References 42 publications

Supporting

Mentioning

268

Contrasting

Unclassified

Order By: Relevance

“…The atmospheric constraints are shown in Figure 1 and Table 1. We confirm the high-confidence detection of H 2 O in a H 2 -rich atmosphere as reported by Benneke et al (2019) and Tsiaras et al (2019). Our abundance estimates are consistent to within 1σ between all four model configurations and with Benneke et al (2019).…”

Section: N/asupporting

confidence: 91%

“…The median H 2 O abundance is 9.3×solar for the full model, case 1. We cannot compare our results with Tsiaras et al (2019) as their retrievals were based on only the HST WFC3 data and used older measurements of the planetary mass and radius which could have biased their inferences.…”

Section: N/amentioning

confidence: 98%

“…However, the extent of such an envelope and the conditions at the interface between the envelope and the underlying interior have not been explored. We note that the mass and radius of the planet have recently been revised (Benneke et al 2019), which may have impacted inferences made using previous values (Cloutier et al 2017;Tsiaras et al 2019).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Interior and Atmosphere of the Habitable-zone Exoplanet K2-18b

Madhusudhan

Nixon²,

Welbanks³

et al. 2020

ApJL

174

View full text Add to dashboard Cite

Exoplanets orbiting M dwarfs present a valuable opportunity for their detection and atmospheric characterisation. This is evident from recent inferences of H 2 O in such atmospheres, including that of the habitable-zone exoplanet K2-18b. With a bulk density between Earth and Neptune, K2-18b may be expected to possess a H/He envelope. However, the extent of such an envelope and the thermodynamic conditions of the interior remain unexplored. In the present work, we investigate the atmospheric and interior properties of K2-18b based on its bulk properties and its atmospheric transmission spectrum. We constrain the atmosphere to be H 2 -rich with a H 2 O volume mixing ratio of 0.02 − 14.8%, consistent with previous studies, and find a depletion of CH 4 and NH 3 , indicating chemical disequilibrium. We do not conclusively detect clouds/hazes in the observable atmosphere. We use the bulk parameters and retrieved atmospheric properties to constrain the internal structure and thermodynamic conditions in the planet. The constraints on the interior allow multiple scenarios between rocky worlds with massive H/He envelopes and water worlds with thin envelopes. We constrain the mass fraction of the H/He envelope to be 6%; spanning 10 −5 for a predominantly water world to ∼ 6% for a pure iron interior. The thermodynamic conditions at the surface of the H 2 O layer range from the super-critical to liquid phases, with a range of solutions allowing for habitable conditions on K2-18b. Our results demonstrate that the potential for habitable conditions is not necessarily restricted to Earth-like rocky exoplanets.

show abstract

Section: N/asupporting

confidence: 91%

Section: N/amentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The Interior and Atmosphere of the Habitable-zone Exoplanet K2-18b

Madhusudhan

Nixon²,

Welbanks³

et al. 2020

ApJL

174

View full text Add to dashboard Cite

show abstract

“…1 in HITRAN 1 ), its main isotopologue H 2 16 O was subject to detailed investigation in the literature. Over the past 100 years, some 200,000 rovibrational lines have been recorded for H 2 16 O (linking nearly 20,000 energy levels 22,23 ) to probe water in the interstellar medium 24 , in exoplanets 25 , on the Sun 26 , and in the Earth's atmosphere, 27 including its greenhouse effect 28,29 . The rovibrational states of H 2 16 O are separated into two subsets, corresponding to the ortho and para nuclear-spin isomers.…”

mentioning

confidence: 99%

Spectroscopic-network-assisted precision spectroscopy and its application to water

et al. 2020

View full text Add to dashboard Cite

Frequency combs and cavity-enhanced optical techniques have revolutionized molecular spectroscopy: their combination allows recording saturated Doppler-free lines with ultrahigh precision. Network theory, based on the generalized Ritz principle, offers a powerful tool for the intelligent design and validation of such precision-spectroscopy experiments and the subsequent derivation of accurate energy differences. As a proof of concept, 156 carefullyselected near-infrared transitions are detected for H 2 16 O, a benchmark system of molecular spectroscopy, at kHz accuracy. These measurements, augmented with 28 extremelyaccurate literature lines to ensure overall connectivity, allow the precise determination of the lowest ortho-H 2 16 O energy, now set at 23.794 361 22(25) cm −1 , and 160 energy levels with similarly high accuracy. Based on the limited number of observed transitions, 1219 calibrationquality lines are obtained in a wide wavenumber interval, which can be used to improve spectroscopic databases and applied to frequency metrology, astrophysics, atmospheric sensing, and combustion chemistry.

show abstract

“…ExoTETHyS is currently being used with synthetic data in order to assess the overall uncertainty in exoplanet spectra obtained with JWST and ARIEL, including the uncertainties in the measured stellar parameters and in the stellar models (e.g., Sarkar, Madhusudhan, & Papageorgiou (2020)). It is also being used for the analysis of real exoplanetary transits (e.g., Tsiaras, Waldmann, Tinetti, Tennyson, & Yurchenko (2019)). Another project is the empirical validation of stellar limb-darkening models through the analysis of high-precision photometric observations obtained, in particular, with Kepler, K2, TESS, CHEOPS and PLATO.…”

Section: Resultsmentioning

confidence: 99%