Ice Giant Systems: The scientific potential of orbital missions to Uranus and Neptune

Fletcher, Leigh N.; Helled, Ravit; Roussos, E.; Jones, G. H.; Charnoz, Sébastien; André, Nicolas; Andrews, David; Bannister, Michele; Bunce, E. J.; Cavalié, T.; Ferri, F.; Fortney, Jonathan J.; Grassi, D.; Griton, Léa; Hartogh, P.; Hueso, R.; Kaspi, Yohai; Lamy, Laurent; Masters, A.; Melin, Henrik; Moses, Julianne I.; Mousis, O.; Nettleman, Nadine; Plainaki, C.; Schmidt, Jürgen; Simon-Miller, A. A.; Tobie, G.; Tortora, Paolo; Tosi, F.; Turrini, D.

doi:10.1016/j.pss.2020.105030

Cited by 48 publications

(48 citation statements)

References 161 publications

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“…The apparent low frequency of convective candidates makes it unlikely that such observations will be obtained from a combination of ground-based AO observations and HST or JWST observations, and the short flybys by Voyager 2 did not produce a dataset large enough to characterize convective candidates. Only observations from an orbiter mission seem able to provide such data [78].…”

Section: (B) Convective Activity In Neptunementioning

confidence: 99%

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Convective storms and atmospheric vertical structure in Uranus and Neptune

Hueso

Guillot

Sánchez‐Lavega

2020

Phil. Trans. R. Soc. A.

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The ice giants Uranus and Neptune have hydrogen-based atmospheres with several constituents that condense in their cold upper atmospheres. A small number of bright cloud systems observed in both planets are good candidates for moist convective storms, but their observed properties (size, temporal scales and cycles of activity) differ from moist convective storms in the gas giants. These clouds and storms are possibly due to methane condensation and observations also suggest deeper clouds of hydrogen sulfide (H 2 S) at depths of a few bars. Even deeper, thermochemical models predict clouds of ammonia hydrosulfide (NH 4 SH) and water at pressures of tens to hundreds of bars, forming extended deep weather layers. Because of hydrogen’s low molecular weight and the high abundance of volatiles, their condensation imposes a strongly stabilizing vertical gradient of molecular weight larger than the equivalent one in Jupiter and Saturn. The resulting inhibition of vertical motions should lead to a moist convective regime that differs significantly from the one occurring on nitrogen-based atmospheres like those of Earth or Titan. As a consequence, the thermal structure of the deep atmospheres of Uranus and Neptune is not well understood. Similar processes might occur at the deep water cloud of Jupiter in Saturn, but the ice giants offer the possibility to study these physical aspects in the upper methane cloud layer. A combination of orbital and in situ data will be required to understand convection and its role in atmospheric dynamics in the ice giants, and by extension, in hydrogen atmospheres including Jupiter, Saturn and giant exoplanets. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems’.

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Section: (B) Convective Activity In Neptunementioning

confidence: 99%

“…Modern explorations of possible mission scenarios to the ice giants Uranus and Neptune [1] [2][3][4] have motivated a revision of what we know about these planets and their planetary systems. Recent reviews explore their atmospheric dynamics [5], mean circulation patterns [6] and vertical structure [5,7].…”

Section: Introductionmentioning

confidence: 99%

Convective storms and atmospheric vertical structure in Uranus and Neptune

Hueso

Guillot

Sánchez‐Lavega

2020

Phil. Trans. R. Soc. A.

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“…In that respect, measurements in the radiation belts of Uranus and Neptune, sampled only once by the Voyager 2 spacecraft, should definitely be part of any future attempt to explore the two planets [Fletcher et al 2019]. Saturn's radiation belts were surveyed in depth thanks to the 13-year Cassini mission at the Kronian system.…”

Section: Executive Summarymentioning

confidence: 99%

“…Planned or ongoing missions would add to that: the limits of radiation belt formation can be exploited with Bepi-Colombo at the weakly magnetized Mercury, and JUICE at Ganymede's mini-magnetosphere [Eviatar et al 2000]. Potential extension of such observations to Uranus or Neptune [Fletcher et al 2019] would allow us to explore radiation belts across a variety of environments and scales. X-ray imagers, following their application on SMILE and Bepi-Colombo [Benkhoff et al 2010;Branduardi-Raymont et al 2018], will become readily available for Jupiter missions and open a new are in the exploration of planetary magnetospheres.…”

Section: Comparative Studiesmentioning

confidence: 99%

The in-situ exploration of Jupiter's radiation belts

Roussos¹

2020

Preprint

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<p>Jupiter has the most energetic and complex radiation belts in our solar system. Their hazardous environment is the reason why so many spacecraft avoid rather than investigate them, and explains how they have kept many of their secrets so well hidden, despite having been studied for decades. We believe that these secrets are worth unveiling, as Jupiter&#8217;s radiation belts and the vast magnetosphere that encloses them constitute an unprecedented physical laboratory, suitable for both interdisciplinary and novel scientific investigations: From studying fundamental high energy plasma physics processes which operate throughout the universe, such as adiabatic charged particle acceleration and nonlinear wave-particle interactions; to exploiting the astrobiological consequences of energetic particle radiation. The in-situ exploration of the uninviting environment of Jupiter&#8217;s radiation belts presents us with many challenges in mission design, science planning, instrumentation and technology development. We address these challenges by reviewing the different options that exist for direct and indirect observation of this unique system. We stress the need for new instruments, the value of synergistic Earth and Jupiter-based remote sensing and in-situ investigations, and the vital importance of multi-spacecraft, in-situ measurements. While simultaneous, multi-point in-situ observations have long become the standard for exploring electromagnetic interactions in the inner solar system, they have never taken place at Jupiter or any strongly magnetized planet besides Earth. We conclude that a dedicated multi-spacecraft mission to Jupiter&#8217;s radiation belts is an essential and obvious way forward. Besides guaranteeing many discoveries and outstanding progress in our understanding of planetary radiation belts, it offers a number of opportunities for interdisciplinary science investigations. For all these reasons, the exploration of Jupiter&#8217;s radiation belts deserves to be given a high priority in the future exploration of our solar system. A White Paper on this subject was submitted in response to ESA's Voyage 2050 call.</p>

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“…If Jupiter Gravity Assist (JGA) is a requirement for the delivery of sufficient spacecraft mass into the system, then a recent NASA-ESA joint study described by Hofstadter et al [48] highlighted optimal launches to Neptune in 2029-2030, and a wider window for Uranus in the early 2030s (although non-JGA trajectories are available [49]). These would have missions arriving in the 2040s, as Uranus approaches northern autumnal equinox (2050) and Neptune reaches northern spring equinox (2046) [15]. Such a trajectory would also allow a spacecraft to visit other solar system objects (such as Centaurs) during the cruise phase, as well as observing the solar wind conditions over a large range of heliocentric distances [15,49,50].…”

Section: Future Missions To the Ice Giantsmentioning

confidence: 99%

Ice giant system exploration in the 2020s: an introduction

Fletcher

Simon-Miller

Hofstadter

et al. 2020

Phil. Trans. R. Soc. A.

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The international planetary science community met in London in January 2020, united in the goal of realizing the first dedicated robotic mission to the distant ice giants, Uranus and Neptune, as the only major class of solar system planet yet to be comprehensively explored. Ice-giant-sized worlds appear to be a common outcome of the planet formation process, and pose unique and extreme tests to our understanding of exotic water-rich planetary interiors, dynamic and frigid atmospheres, complex magnetospheric configurations, geologically-rich icy satellites (both natural and captured), and delicate planetary rings. This article introduces a special issue on ice giant system exploration at the start of the 2020s. We review the scientific potential and existing mission design concepts for an ambitious international partnership for exploring Uranus and/or Neptune in the coming decades. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems’.

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Ice Giant Systems: The scientific potential of orbital missions to Uranus and Neptune

Cited by 48 publications

References 161 publications

Convective storms and atmospheric vertical structure in Uranus and Neptune

Convective storms and atmospheric vertical structure in Uranus and Neptune

The in-situ exploration of Jupiter's radiation belts

Ice giant system exploration in the 2020s: an introduction

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