Hydrogen Halides on Jupiter and Saturn

Showman, Adam P.

doi:10.1006/icar.2001.6614

Cited by 16 publications

(23 citation statements)

References 64 publications

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“…Then, for a NH 3 mole fraction of 1.8 × 10 −5 at 600 mbar, we derived equilibrium mole fraction of ∼ 10 −37 and ∼ 10 −46 for HF and HCl, respectively. This result confirms the expectations of Showman (2001) that hydrogen halide chemistry should not depart at detectable levels from thermodynamic equilibrium. In addition, we found that HBr is subsolar at a 2-σ confidence level with a mole fraction of 6.6 × 10 −10 , suggesting also the condensation of this gas.…”

Section: Moleculesupporting

confidence: 91%

“…This is much shorter than the estimated ∼ 10 8 -s overturn timescale of the jovian upper troposphere. Showman (2001) showed also that, even in the absence of foreign particles, self-nucleation should prevent observable supersaturation. Hence, we do not expect the hydrogen halides chemistry to depart significantly from equilibrium.…”

Section: Introductionmentioning

confidence: 95%

“…This situation occurs when the loss timescale of a given species is longer than the convective mixing time. Showman (2001) explored the kinetics of hydrogen halides condensation, and calculated loss timescales between ∼ 10 3 -10 5 s for realistic cloud densities and particle sizes. This is much shorter than the estimated ∼ 10 8 -s overturn timescale of the jovian upper troposphere.…”

Section: Introductionmentioning

confidence: 99%

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

Fouchet¹,

Orton²,

Irwin³

et al. 2004

Icarus

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Section: Moleculesupporting

confidence: 91%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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

Fouchet¹,

Orton²,

Irwin³

et al. 2004

Icarus

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“…externally sourced HCl could avoid removal by reactions with tropospheric 36 ammonia and potentially persist in observable quantities in the upper strato-37 3 sphere and mesosphere (Showman, 2001). 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).…”

mentioning

confidence: 99%

“…where K(z) is the eddy diffusion coefficient, n(z) is the number density of HCl, H(z) is the atmospheric scale height (RT/Mg), and T (z) is the tem-322 perature (Showman, 2001;Chamberlain and Hunten, 1987). The bottom 323 15 boundary condition was defined by:…”

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

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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...

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