Future destabilisation of Titan as a result of Saturn’s tilting

Saillenfest, Melaine; Lari, Giacomo

doi:10.1051/0004-6361/202141467

Cited by 4 publications

(27 citation statements)

References 51 publications

(158 reference statements)

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“…As a result, this new scenario would not require a particularly massive satellite, nor a particularly high orbital inclination for the planet. This tilting mechanism was actually proven to work for Saturn on its current orbit, and it is expected to work as well for any giant planet of the solar system, should it have the adequate long-range migrating satellite (Saillenfest & Lari 2021).…”

Section: Introductionmentioning

confidence: 94%

“…As shown by Saillenfest & Lari (2021), the influence of a given regular satellite on the spin-axis precession of its host planet critically depends on its non-dimensional 'mass parameter' η, defined by…”

Section: Tilting Mechanismmentioning

confidence: 99%

“…Independently of Uranus and Neptune, Saillenfest & Lari (2021) have recently described a mechanism through which a migrating satellite can tilt an initially small-obliquity planet up to over ε = 90 • with almost no modification to its spin rate. Their study was prompted by the works of Lainey et al (2009Lainey et al ( , 2020, who discovered that the orbital expansion of satellites around Jupiter and Saturn are much faster than previously thought, indicating that efficient mechanisms of tidal dissipation can take place not only in terrestrial planets, as it was known for the Earth-Moon system, but also in giant planets.…”

Section: Introductionmentioning

confidence: 99%

“…Such a fast satellite migration has been found to deeply affect the spin-axis dynamics of Jupiter and Saturn (see Lari et al 2020;Saillenfest et al 2020Saillenfest et al , 2021a. In fact, while exploring the future evolution of Saturn and Titan, Saillenfest & Lari (2021) have shown that if a satellite substantially migrates inwards or outwards, then its influence on the spin-axis precession of its host planet changes over time in a way that is intimately linked to the properties of its equilibrium orbital plane, called 'Laplace plane' (Tremaine et al 2009). The Laplace plane is well defined everywhere in the parameter space, except in a specific point, called S 1 , where it degenerates into a continuum of equilibria.…”

Section: Introductionmentioning

confidence: 99%

“…Depending on the migration rate of the satellite, this whole process can take place over the whole lifetime of the planetary system. Importantly, S 1 is surrounded by an unstable region which may lead to the destruction of the satellite once the tilting is achieved (Tremaine et al 2009;Saillenfest & Lari 2021). New satellites could then be formed from the leftover debris disc (Crida & Charnoz 2012).…”

Section: Introductionmentioning

confidence: 99%

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Tilting Uranus via the migration of an ancient satellite

Saillenfest

Rogoszinski

Lari

et al. 2022

A&A

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Context. The 98 • -obliquity of Uranus is commonly attributed to giant impacts that occurred at the end of the planetary formation. This picture, however, is not devoid of weaknesses. Aims. On a billion-year timescale, the tidal migration of the satellites of Jupiter and Saturn has been shown to strongly affect their spin-axis dynamics. We aim to revisit the scenario of tilting Uranus in light of this mechanism. Methods. We analyse the precession spectrum of Uranus and identify the candidate secular spin-orbit resonances that could be responsible for the tilting. We determine the properties of the hypothetical ancient satellite required for a capture and explore the dynamics numerically.Results. If it migrates over 10 Uranus' radii, a single satellite with minimum mass 4 × 10 −4 Uranus' mass is able to tilt Uranus from a small obliquity and make it converge towards 90 • . In order to achieve the tilting in less than the age of the Solar System, the mean drift rate of the satellite must be comparable to the Moon's current orbital expansion. Under these conditions, simulations show that Uranus is readily tilted over 80 • . Beyond this point, the satellite is strongly destabilised and triggers a phase of chaotic motion for the planet's spin axis. The chaotic phase ends when the satellite collides into the planet, ultimately freezing the planet's obliquity in either a prograde, or plainly retrograde state (as Uranus today). Spin states resembling that of Uranus can be obtained with probabilities as large as 80%, but a bigger satellite is favoured, with mass 1.7 × 10 −3 Uranus' mass or more. Yet, a smaller ancient satellite is not categorically ruled out, and there is room for improving this basic scenario in future studies. Interactions among several pre-existing satellites is a promising possibility. Conclusions. The conditions required for the tilting seem broadly realistic, but it remains to be determined whether Uranus could have hosted a big primordial satellite subject to substantial tidal migration. The efficiency of tidal energy dissipation within Uranus is required to be much higher than traditionally assumed, more in line with that measured for the migration of Titan. Hints about these issues would be given by a measure of the expansion rate of Uranus' main satellites.

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Section: Introductionmentioning

confidence: 94%

Section: Tilting Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tilting Uranus via the migration of an ancient satellite

Saillenfest

Rogoszinski

Lari

et al. 2022

A&A

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Long-Term Evolution of the Saturnian System

Ćuk,

El Moutamid,

Lari

et al. 2024

Space Sci Rev

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Here we present the current state of knowledge on the long-term evolution of Saturn’s moon system due to tides within Saturn. First we provide some background on tidal evolution, orbital resonances and satellite tides. Then we address in detail some of the present and past orbital resonances between Saturn’s moons (including the Enceladus-Dione and Titan-Hyperion resonances) and what they can tell us about the evolution of the system. We also present the current state of knowledge on the spin-axis dynamics of Saturn: we discuss arguments for a (past or current) secular resonance of Saturn’s spin precession with planetary orbits, and explain the links of this resonance to the tidal evolution of Titan and a possible recent cataclysm in the Saturnian system. We also address how the moons’ orbital evolution, including resonances, affects the evolution of their interiors. Finally, we summarize the state of knowledge about the Saturnian system’s long-term evolution and discuss prospects for future progress.

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Oblique rings from migrating exomoons: A possible origin for long-period exoplanets with enlarged radii

Saillenfest¹,

Sulis²,

Charpentier³

et al. 2023

A&A

Self Cite

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Context. The extremely low density of several long-period exoplanets in mature systems is still unexplained - with HIP 41378 f being archetypical of this category. It has been proposed that such planets could actually have normal densities but be surrounded by a ring observed approximately face on, mimicking the transit depth of a puffy planet. This configuration would imply that the equator of the planet is nearly perpendicular to its orbit plane, which is at odds with the formation process of gas giants. Yet, in the context of the Solar System planets, it has recently been shown that after gigayears of evolution, the tidal migration of a moon can naturally lead to a very tilted planet with a ring. Aims. As exomoons are expected to be ubiquitous around giant exoplanets, this mechanism may be responsible for the anomalous radii of some observed exoplanets. In preparation for the future discoveries of the PLATO mission, we present a simple method for checking the plausibility of this mechanism for a given exoplanet. Methods. Analytical formulas give the probability density function of the relevant precession harmonics of the planet. For each harmonic, simple criteria set the moon mass and other properties required for the mechanism to operate. Results. We applied this methodology to HIP 41378 f, and we show that in order to reproduce the observed configuration, a hypothetical former moon should have had a moon-to-planet mass ratio of a few times 10−4 (i.e. roughly the mass of our Moon) and have migrated over a distance of a few planet’s radii on a gigayear timescale. These orders of magnitude match the properties of moons expected to exist around gaseous exoplanets. Conclusions. We conclude that the migration of a former moon is a viable formation pathway for the proposed ring and tilt of HIP 41378 f. This example strengthens the ring hypothesis and motivates its application to other promising targets.

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Future destabilisation of Titan as a result of Saturn’s tilting

Cited by 4 publications

References 51 publications

Tilting Uranus via the migration of an ancient satellite

Tilting Uranus via the migration of an ancient satellite

Long-Term Evolution of the Saturnian System

Oblique rings from migrating exomoons: A possible origin for long-period exoplanets with enlarged radii

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