Uranus and Neptune are key to understand planets with hydrogen atmospheres

Guillot, T.

doi:10.1007/s10686-021-09812-x

Cited by 12 publications

(5 citation statements)

References 93 publications

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“…Ice giants also provide a unique regime to understand moist convection in giant planets (Hofstadter et al 2020;Guillot 2022) and an opportunity to test the self-limited moist convection and convective inhibition proposed in this study. The vertical temperature and composition structure at the CH 4 condensation level can be constrained by radio occultation from the orbiter (Lindal et al 1987;Lindal 1992).…”

Section: Implication For Uranus Orbiter and Probementioning

confidence: 93%

Heat-flux-limited Cloud Activity and Vertical Mixing in Giant Planet Atmospheres with an Application to Uranus and Neptune

Ge 葛,

Li,

Zhang

et al. 2024

Planet. Sci. J.

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Storms operated by moist convection and the condensation of CH4 or H2S have been observed on Uranus and Neptune. However, the mechanism of cloud formation, thermal structure, and mixing efficiency of ice giant weather layers remains unclear. In this paper, we show that moist convection is limited by heat transport on giant planets, especially on ice giants where planetary heat flux is weak. Latent heat associated with condensation and evaporation can efficiently bring heat across the weather layer through precipitations. This effect was usually neglected in previous studies without a complete hydrological cycle. We first derive analytical theories and show that the upper limit of cloud density is determined by the planetary heat flux and microphysics of clouds but is independent of the atmospheric composition. The eddy diffusivity of moisture depends on the planetary heat fluxes, atmospheric composition, and surface gravity but is not directly related to cloud microphysics. We then conduct convection- and cloud-resolving simulations with SNAP to validate our analytical theory. The simulated cloud density and eddy diffusivity are smaller than the results acquired from the equilibrium cloud condensation model and mixing length theory by several orders of magnitude but consistent with our analytical solutions. Meanwhile, the mass-loading effect of CH4 and H2S leads to superadiabatic and stable weather layers. Our simulations produced three cloud layers that are qualitatively similar to recent observations. This study has important implications for cloud formation and eddy mixing in giant planet atmospheres in general and observations for future space missions and ground-based telescopes.

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Section: Implication For Uranus Orbiter and Probementioning

confidence: 93%

Heat-flux-limited Cloud Activity and Vertical Mixing in Giant Planet Atmospheres with an Application to Uranus and Neptune

Ge 葛,

Li,

Zhang

et al. 2024

Planet. Sci. J.

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“…Possible Uranian Ar, Kr, and Xe abundances are scaled from Jupiter at a nominal enhancement of 50 times, but over a very wide range extending from the small 2.5 times Jovian amplification to an upper bound of 100 times. We have not scaled NH 3 or H 2 S from Jupiter, as neither behave simply enough at Uranian temperatures to yield trustworthy bulk abundances from remote observations (Guillot 2022). Nitrogen and sulfur will be targets for in situ measurements with the Uranus Probe.…”

Section: Uranus Inspired By Jupitermentioning

confidence: 99%

Noble Gas Planetology and the Xenon Clouds of Uranus

Zahnle

2024

Planet. Sci. J.

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Noble gases provide tracers of cosmic provenance that are accessible to a future Uranus atmospheric probe. Argon and krypton are expected to be well mixed on Uranus with respect to H2 and He, although condensation at the winter pole may be possible. The Ar/H2 and Ar/Kr ratios address whether the materials accreted by Uranus resembled the extremely cold materials accreted by Jupiter’s atmosphere, whether they were warmer, like comet 67P/Churyumov–Gerasimenko (67P/C-G), or whether Uranus is like neither. Xenon condenses as an ice, probably on methane ice, in Uranus’s upper troposphere. Condensation may complicate the interpretation of Xe/H2, but it also presents an opportunity to collect concentrated xenon samples suitable for measuring isotopes. Solar system Xe tracks three distinct nucleosynthetic xenon reservoirs, one evident in the Sun and in chondritic meteorites, a second in refractory presolar grains, and a third evident in comet 67P/C-G and in Earth’s air. The first and third reservoirs appear to have been captured from different clouds of gas. The two gases do not appear to have been well mixed; moreover, the high 129Xe/132Xe ratio in 67P/C-G implies that the gas was captured before the initial nucleosynthetic complement of 129I (15.7 Myr half-life) had decayed. Xenon’s isotopic peculiarities, if seen in Uranus, could usefully upset our understanding of planetary origins. Krypton’s isotopic anomalies are more subtle and may prove hard to measure. There is a slight chance that neon and helium fractionations can be used to constrain how Uranus acquired its nebular envelope.

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“…Yet, the current measurements of Uranus and Neptune are poor, and consequently, the observations cannot distinguish between the suggested models, and there is a great degeneracy in terms of the shape of the composition gradients and their content. As of today, more observations are needed in order to achieve further progress in understanding the interiors of the two planets [136][137][138].…”

Section: Uranus and Neptune: Ice-rock Mixtures And Non Adiabatic Inte...mentioning

confidence: 99%

Interior and Evolution of the Giant Planets

Miguel

Vazan

2023

Remote Sensing

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The giant planets were the first to form and hold the key to unveiling the solar system’s formation history in their interiors and atmospheres. Furthermore, the unique conditions present in the interiors of the giant planets make them natural laboratories for exploring different elements under extreme conditions. We are at a unique time to study these planets. The missions Juno to Jupiter and Cassini to Saturn have provided invaluable information to reveal their interiors like never before, including extremely accurate gravity data, atmospheric abundances and magnetic field measurements that revolutionised our knowledge of their interior structures. At the same time, new laboratory experiments and modelling efforts also improved, and statistical analysis of these planets is now possible to explore all the different conditions that shape their interiors. We review the interior structure of Jupiter, Saturn, Uranus and Neptune, including the need for inhomogeneous structures to explain the data, the problems unsolved and the effect that advances in our understanding of their internal structure have on their formation and evolution.

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Uranus and Neptune are key to understand planets with hydrogen atmospheres

Cited by 12 publications

References 93 publications

Heat-flux-limited Cloud Activity and Vertical Mixing in Giant Planet Atmospheres with an Application to Uranus and Neptune

Heat-flux-limited Cloud Activity and Vertical Mixing in Giant Planet Atmospheres with an Application to Uranus and Neptune

Noble Gas Planetology and the Xenon Clouds of Uranus

Interior and Evolution of the Giant Planets

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