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تسجيل مستخدم جديدGiant Planets
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Tristan Guillot
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We review the interior structure and evolution of Jupiter, Saturn, Uranus and Neptune, and giant exoplanets with particular emphasis on constraining their global composition. Compared to the first edition of this review, we provide a new discussion of the atmospheric compositions of the solar system giant planets, we discuss the discovery of oscillations of Jupiter and Saturn, the significant improvements in our understanding of the behavior of material at high pressures and the consequences for interior and evolution models. We place the giant planets in our Solar System in context with the trends seen for exoplanets.
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Giant planets are thought to have cores in their deep interiors, and the division into a heavy-element core and hydrogen-helium envelope is applied in both formation and structure models. We show that the primordial internal structure depends on the
planetary growth rate, in particular, the ratio of heavy elements accretion to gas accretion. For a wide range of likely conditions, this ratio is in one-to-one correspondence with the resulting post-accretion profile of heavy elements within the planet. This flux ratio depends sensitively on the assumed solid surface density in the surrounding nebula. We suggest that giant planets cores might not be distinct from the envelope and includes some hydrogen and helium, and the deep interior can have a gradual heavy-element structure. Accordingly, Jupiters core may not be well-defined. Accurate measurements of Jupiters gravitational field by Juno could put constraints on Jupiters core mass. However, as we suggest here, the definition of Jupiters core is complex, and the cores physical properties (mass, density) depend on the actual definition of the core and on its growth history.
In the last few years, the so-called Nice model has got a significant importance in the study of the formation and evolution of the solar system. According to this model, the initial orbital configuration of the giant planets was much more compact th
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. A remarkable example of the superiority of in situ probe measurements was illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases abundances and the precise measurement of the helium mixing ratio were only made available through in situ measurements by the Galileo probe. Here we describe the main scientific goals to be addressed by the future in situ exploration of Saturn, Uranus, and Neptune, placing the Galileo probe exploration of Jupiter in a broader context. An atmospheric entry probe targeting the 10-bar level would yield insight into two broad themes: i) the formation history of the giant planets and that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. An atmospheric probe could represent a significant ESA contribution to a future NASA New Frontiers or flagship mission to be launched toward Saturn, Uranus, and/or Neptune.
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