Upper limits on hydrogen halides in Jupiter from Cassini/CIRS observations

Fouchet, Thierry; Orton, Glenn S.; Irwin, Patrick; Calcutt, S. B.; Nixon, C. A.

doi:10.1016/j.icarus.2004.03.013

Cited by 18 publications

(14 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The latter two are not included in Exo-REM, the condensation of RbCl and CsCl removing less than 0.15% of the Cl, assuming a standard composition. While the NH 4 Cl cloud is, to our knowledge, rarely mentioned in the exoplanet literature, it offers an explanation to the lack of Cl-bearing species in the upper atmosphere of the giant planets of our solar system (Fouchet et al 2004;Teanby et al 2006). Nevertheless, we found that with our nominal model, NH 4 Cl clouds with r = 5 µm -roughly the minimum value found by the Exo-REM self-consistent cloud model on the layer with the most particles -have essentially no impact on the temperature profile and a marginal impact on the visual part of the transmission spectrum 5 , lowering the χ 2 against Benneke et al (2019a) data by ≈ 0.2.…”

Section: Cloudsmentioning

confidence: 98%

1D atmospheric study of the temperate sub-Neptune K2-18b

Blain

Charnay

Bézard

2021

A&A

View full text Add to dashboard Cite

Context. The atmospheric composition of exoplanets with masses between 2 and 10 M ⊕ is poorly understood. In that regard, the sub-Neptune K2-18b, which is subject to Earth-like stellar irradiation, offers a valuable opportunity for the characterisation of such atmospheres. Previous analyses of its transmission spectrum from the Kepler, Hubble (HST), and Spitzer space telescopes data using both retrieval algorithms and forward-modelling suggest the presence of H 2 O and an H 2-He atmosphere, but have not detected other gases, such as CH 4. Aims. We present simulations of the atmosphere of K2-18 b using Exo-REM, our self-consistent 1D radiative-equilibrium model, using a large grid of atmospheric parameters to infer constraints on its chemical composition. Methods. We compared the transmission spectra computed by our model with the above-mentioned data (0.4 to 5 µm), assuming an H 2-He dominated atmosphere. We investigated the effects of irradiation, eddy diffusion coefficient, internal temperature, clouds, C/O ratio, and metallicity on the atmospheric structure and transit spectrum. Results. We show that our simulations favour atmospheric metallicities between 40 and 500 times solar and indicate, in some cases, the formation of H 2 O-ice clouds, but not liquid H 2 O clouds. We also confirm the findings of our previous study, which showed that CH 4 absorption features nominally dominate the transmission spectrum in the HST spectral range. We compare our results with results from retrieval algorithms and find that the H 2 O-dominated spectrum interpretation is either due to the omission of CH 4 absorptions or a strong overfitting of the data. Finally, we investigated different scenarios that would allow for a CH 4-depleted atmosphere. We were able to fit the data to those scenarios, finding, however, that it is very unlikely for K2-18b to have a high internal temperature. A low C/O ratio (≈ 0.01-0.1) allows for H 2 O to dominate the transmission spectrum and can fit the data but so far, this setup lacks a physical explanation. Simulations with a C/O ratio < 0.01 are not able to fit the data satisfactorily.

show abstract

Section: Cloudsmentioning

confidence: 98%

1D atmospheric study of the temperate sub-Neptune K2-18b

Blain

Charnay

Bézard

2021

A&A

View full text Add to dashboard Cite

show abstract

“…In addition to the aforementioned molecules, H 2 Se, H 2 S, and halides (HF, HCl, HBr, HI) are promising candidates (Bézard et al, 1986). Using the strongest lines below 205 cm −1 , Fouchet et al (2004a) A similar analysis using CIRS spectra of Saturn would be useful for comparative studies of these two planets. Thermochemical models predict that halogens in the observable atmosphere should be trapped in the condensed phase as ammonium salts.…”

Section: Atmospheric Gas Compositionmentioning

confidence: 99%

Exploring The Saturn System In The Thermal Infrared: The Composite Infrared Spectrometer

et al. 2004

View full text Add to dashboard Cite

show abstract

“…or HI) on any giant planet has remained elusive (Noll, 1996;Weisstein and 46 Serabyn, 1996; Kerola et al, 1997;Fouchet et al, 2004;Teanby et al, 2006;47 Fletcher et al, 2012). The closest to a positive detection on any of the giant 48 planets was by Weisstein and Serabyn (1996) who produced a tentative de- spectral resolution and reduced sensitivities to narrow spectral lines.…”

mentioning

confidence: 99%

Constraints on Jupiter׳s stratospheric HCl abundance and chlorine cycle from Herschel/HIFI

Teanby

Showman

Fletcher

et al. 2014

Planetary and Space Science

View full text Add to dashboard Cite

Detection of HCl on Jupiter would provide insight into the chlorine cycle and external elemental fluxes on giant planets, yet so far has not been possible. Here we present the most sensitive search for Jupiter's stratospheric HCl to date using observations of the 625.907 and 1876.221 GHz spectral lines with Herschel's HIFI instrument. HCl was not detected, but we determined the most stringent upper limits so far, improving on previous studies by two orders of magnitude. If HCl is assumed to be uniformly mixed, with a constant volume mixing ratio above the 1 mbar pressure level and has zero abundance below, we obtain a 3-sigma upper limit of 0.056 ppb; in contrast, if we assume uniform mixing above the 1~mbar level and allow a non-zero but downward-decreasing abundance from 1~mbar to the troposphere based on eddy diffusion, we obtain a 3-sigma upper limit of 0.024 ppb. This is below the abundance expected for a solar composition source, such as comets, and implies that upper atmosphere HCl loss processes are important. We investigated aerosol scavenging using a simple diffusion model and conclude that it could be a very effective mechanism for HCl removal. Transient scavenging by stratospheric NH3 from impacts is another potentially important loss mechanism. This suggests that it is extremely unlikely that HCl is present in sufficient quantities to be detectable in the near future. We summarise the implications for Jupiter's chlorine cycle and conclude that based on a combination of our observations and previous studies of external oxygen supply, a solar composition external source for Jupiter's chlorine combined with stratospheric scavenging by aerosols and NH3 appears the most plausible. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 AbstractDetection of HCl on Jupiter would provide insight into the chlorine cycle and external elemental fluxes on giant planets, yet so far has not been possible. Here we present the most sensitive search for Jupiter's stratosphericHCl to date using observations of the 625.907 and 1876.221 GHz spectral lines with Herschel's HIFI instrument. HCl was not detected, but we determined the most stringent upper limits so far, improving on previous studies by two orders of magnitude. If HCl is assumed to be uniformly mixed, with a constant volume mixing ratio above the 1 mbar pressure level and has zero abundance below, we obtain a 3-σ upper limit of 0.056 ppb; in contrast, if we assume uniform mixing above the 1 mbar level and allow a non-zero but downward-decreasing abundance from 1 mbar to the troposphere based on eddy diffusion, we obtain a 3-σ upper limit of 0.024 ppb. This is below the abundance expected for a solar composition source, such as comets, and 6 Herschel is an ESA space observatory with science instruments provided by Europeanled Principal Investigator consortia and wit...

show abstract

Upper limits on hydrogen halides in Jupiter from Cassini/CIRS observations

Cited by 18 publications

References 26 publications

1D atmospheric study of the temperate sub-Neptune K2-18b

1D atmospheric study of the temperate sub-Neptune K2-18b

Exploring The Saturn System In The Thermal Infrared: The Composite Infrared Spectrometer

Constraints on Jupiter׳s stratospheric HCl abundance and chlorine cycle from Herschel/HIFI

Contact Info

Product

Resources

About