Neptune’s carbon monoxide profile and phosphine upper limits from Herschel/SPIRE: Implications for interior structure and formation

Teanby, N. A.; Irwin, Patrick; Moses, J. I.

doi:10.1016/j.icarus.2018.09.014

Cited by 21 publications

(52 citation statements)

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“…60 K [41], suggesting an emission level of 0.5-1 bar and placing the R-C boundary at a similar level. These inferences based on lapse rate are also entirely consistent with reduced mixing in the upper troposphere as suggested by the non-detection of disequilibrium species PH 3 in the upper troposphere [25].…”

Section: (A) Temperature Thermal Emission and Mixingsupporting

confidence: 78%

“…Therefore, mixing in the upper troposphere is currently not well constrained, either by photochemical model comparisons or the emitted heat flux. Further insight into mixing can be gained by comparing the measured tropospheric lapse rate to that expected from adiabatic advection [25]. If the measured lapse rate is greater than the adiabatic lapse rate then the atmosphere can be expected to be unstable with significant mixing occurring.…”

Section: (A) Temperature Thermal Emission and Mixingmentioning

confidence: 99%

“…However, an approximate comparison can still be made. Figure 1c compares the observed lapse rate (−dT/dz) from the composite temperature profile in [25], which is a combination of the radio occultation royalsocietypublishing.org/journal/rsta Phil. Trans.…”

Section: (A) Temperature Thermal Emission and Mixingmentioning

confidence: 99%

“…Recent work shows there may be significant mixing near internal interfaces, leading to more continuous density profiles [9,20,22]. This widens the range of possible internal structures significantly and leaves open the question of whether silicate-gas mixtures or ice mixtures dominate Uranus and Neptune's interiors [9,[24][25][26].…”

Section: Introductionmentioning

confidence: 99%

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Neptune and Uranus: ice or rock giants?

Teanby

Irwin

Moses

et al. 2020

Phil. Trans. R. Soc. A.

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Existing observations of Uranus and Neptune’s fundamental physical properties can be fitted with a wide range of interior models. A key parameter in these models is the bulk rock:ice ratio and models broadly fall into ice-dominated (ice giant) and rock-dominated (rock giant) categories. Here we consider how observations of Neptune’s atmospheric temperature and composition (H 2 , He, D/H, CO, CH 4 , H 2 O and CS) can provide further constraints. The tropospheric CO profile in particular is highly diagnostic of interior ice content, but is also controversial, with deep values ranging from zero to 0.5 parts per million. Most existing CO profiles imply extreme O/H enrichments of >250 times solar composition, thus favouring an ice giant. However, such high O/H enrichment is not consistent with D/H observations for a fully mixed and equilibrated Neptune. CO and D/H measurements can be reconciled if there is incomplete interior mixing (ice giant) or if tropospheric CO has a solely external source and only exists in the upper troposphere (rock giant). An interior with more rock than ice is also more compatible with likely outer solar system ice sources. We primarily consider Neptune, but similar arguments apply to Uranus, which has comparable C/H and D/H enrichment, but no observed tropospheric CO. While both ice- and rock-dominated models are viable, we suggest a rock giant provides a more consistent match to available atmospheric observations. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems’.

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Section: (A) Temperature Thermal Emission and Mixingsupporting

confidence: 78%

Section: (A) Temperature Thermal Emission and Mixingmentioning

confidence: 99%

Section: (A) Temperature Thermal Emission and Mixingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Neptune and Uranus: ice or rock giants?

Teanby

Irwin

Moses

et al. 2020

Phil. Trans. R. Soc. A.

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“…This difference primarily results from their different tropospheric CO abundances. While Teanby et al (2019) recently propose from their Herschel-SPIRE data a model without any tropospheric CO in Neptune, i.e., very similar to Uranus, their results probably lack sensitivity in the upper troposphere to make this result robust. Moreno et al (2011) show in a preliminary combined analysis of Herschel-SPIRE and IRAM-30 m data, including the CO(1-0) line that is most sensitive to the tropospheric CO, that the tropospheric CO in Neptune was 0.20˘0.05 ppm.…”

Section: Implications For the Formation Of Uranus And Neptunementioning

confidence: 89%

New chemical scheme for giant planet thermochemistry

Venot

Cavalié

Bounaceur

et al. 2020

A&A

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Context. Several chemical networks have been developed to study warm (exo)planetary atmospheres. The kinetics of the reactions related to the methanol chemistry included in these schemes have been questioned. Aims. The goal of this paper is to update the methanol chemistry for such chemical networks based on recent publications in the combustion literature. We also aim to study the consequences of this update on the atmospheric compositions of (exo)planetary atmospheres and brown dwarfs. Methods. We performed an extensive review of combustion experimental studies and revisited the sub-mechanism describing methanol combustion in a scheme published in 2012. The updated scheme involves 108 species linked by a total of 1906 reactions. We then applied our 1D kinetic model with this new scheme to the case studies HD 209458b, HD 189733b, GJ 436b, GJ 1214b, ULAS J1335+11, Uranus, and Neptune; we compared these results with those obtained with the former scheme. Results. The update of the scheme has a negligible impact on the atmospheres of hot Jupiters. However, the atmospheric composition of warm Neptunes and brown dwarfs is modified sufficiently to impact observational spectra in the wavelength range in which James Webb Space Telescope will operate. Concerning Uranus and Neptune, the update of the chemical scheme modifies the abundance of CO and thus impacts the deep oxygen abundance required to reproduce the observational data. For future 3D kinetics models, we also derived a reduced scheme containing 44 species and 582 reactions. Conclusions. Chemical schemes should be regularly updated to maintain a high level of reliability on the results of kinetic models and be able to improve our knowledge of planetary formation.

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Ice Giant Circulation Patterns: Implications for Atmospheric Probes

et al. 2020

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Atmospheric circulation patterns derived from multi-spectral remote sensing can serve as a guide for choosing a suitable entry location for a future in situ probe mission to the Ice Giants. Since the Voyager-2 flybys in the 1980s, three decades of observations from ground- and space-based observatories have generated a picture of Ice Giant circulation that is complex, perplexing, and altogether unlike that seen on the Gas Giants. This review seeks to reconcile the various competing circulation patterns from an observational perspective, accounting for spatially-resolved measurements of: zonal albedo contrasts and banded appearances; cloud-tracked zonal winds; temperature and para-H2 measurements above the condensate clouds; and equator-to-pole contrasts in condensable volatiles (methane, ammonia, and hydrogen sulphide) in the deeper troposphere. These observations identify three distinct latitude domains: an equatorial domain of deep upwelling and upper-tropospheric subsidence, potentially bounded by peaks in the retrograde zonal jet and analogous to Jovian cyclonic belts; a mid-latitude transitional domain of upper-tropospheric upwelling, vigorous cloud activity, analogous to Jovian anticyclonic zones; and a polar domain of strong subsidence, volatile depletion, and small-scale (and potentially seasonally-variable) convective activity. Taken together, the multi-wavelength observations suggest a tiered structure of stacked circulation cells (at least two in the troposphere and one in the stratosphere), potentially separated in the vertical by (i) strong molecular weight gradients associated with cloud condensation, and by (ii) transitions from a thermally-direct circulation regime at depth to a wave- and radiative-driven circulation regime at high altitude. The inferred circulation can be tested in the coming decade by 3D numerical simulations of the atmosphere, and by observations from future world-class facilities. The carrier spacecraft for any probe entry mission must ultimately carry a suite of remote-sensing instruments capable of fully constraining the atmospheric motions at the probe descent location.

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Neptune’s carbon monoxide profile and phosphine upper limits from Herschel/SPIRE: Implications for interior structure and formation

Cited by 21 publications

References 65 publications

Neptune and Uranus: ice or rock giants?

Neptune and Uranus: ice or rock giants?

New chemical scheme for giant planet thermochemistry

Ice Giant Circulation Patterns: Implications for Atmospheric Probes

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