Context. The strong tidal dissipation in the couple Jupiter-Io is spread to all the moons involved in the Laplace resonance (Io, Europa, and Ganymede), leading to a migration of their orbits.
Aims. We aim to characterize the future behavior of the Galilean satellites over the Solar System lifetime and to quantify the stability of the Laplace resonance. Since tidal dissipation makes possible the exit from the current resonances or capture into new ones, we investigate the capture of Callisto into resonance.
Methods. We perform hundreds of propagations using an improved version of a recent semi-analytical model. As Ganymede moves outwards, it approaches the 2:1 resonance with Callisto, inducing a temporary chaotic motion in the system. For this reason, we draw a statistical picture of the outcome of the resonant encounter.
Results. The system can settle into two distinct outcomes: A) a chain of three 2:1 two-body resonances (Io-Europa, Europa-Ganymede and Ganymede-Callisto), or B) a resonant chain involving the 2:1 two-body resonance Io-Europa plus at least one pure 4:2:1 three-body resonance, most frequently between Europa, Ganymede and Callisto. In case A (56\% of the simulations), the Laplace resonance is always preserved and the eccentricities remain confined to small values below 0.01. In case B (44\% of the simulations), the Laplace resonance is generally disrupted and the eccentricities of Ganymede and Callisto can increase up to about 0.1, making this configuration unstable and driving the system into new resonances.
Conclusion. From our results, the capture of Callisto into resonance appears to be extremely likely (100\% of our simulations). Assuming the most recent estimate of the dissipation between Io and Jupiter, the resonant encounter happens at about 1.5 Gyrs from now. Therefore, the stability of the Laplace resonance is guaranteed at least up to about 1.5 Gyrs.
The dynamics of the innermost Galilean satellites (Io, Europa and Ganymede) is characterised by a chain of mean motion resonances, called Laplace resonance, and by a strong tidal dissipation that causes wide variations of their semi-major axes over large timescales. The precise history of energy dissipation in the Jovian system is not known, but several theories have been proposed. Tidal resonance locking states that big outer moons can also migrate fast. If this is the case for Callisto, then it should have crossed the 2:1 mean motion resonance with Ganymede in the past, affecting the motion …
A key feature of the Galilean satellite system is its monotonic decrease in bulk density with distance from Jupiter, indicating an ice mass fraction that is zero in the innermost moon Io, and about half in the outer moons Ganymede and Callisto. Jupiter formation models, and perhaps the Juno spacecraft water measurements, are consistent with the possibility that the Jovian system may have formed, at least partly, from ice-poor material. And yet, models of the formation of the Galilean satellites usually assume abundant water ice in the system. Here, we investigate the possibility that the Jovia…
We investigated whether sulfur-bearing species are present on the icy Galilean moon Callisto by analyzing eight near-infrared reflectance spectra collected over a wide range of sub-observer longitudes. We measured the band areas and depths of a 4-micron feature in these spectra, which has been attributed to sulfur dioxide (SO2), as well as carbonates, in previously collected datasets of this moon. All eight spectra we collected display the 4-micron band. The four spectra collected over Callisto's leading hemisphere display significantly stronger 4-micron bands compared to the four trailing hem…
The tenuous atmospheres of the Galilean satellites are sourced from their surfaces and produced by a combination of plasma-surface interactions and thermal processes. Though thin, these atmospheres can be studied via their auroral emissions, and most work to date has focused on their aurora at UV wavelengths. Here we present the first detections of Ganymede's and Callisto's optical aurorae, as well detections of new optical auroral lines at Europa, based on observations of the targets over ten Jupiter eclipses from 1998 to 2021 with Keck/HIRES. We present measurements of OI emission at 6300/63…
The origins of the Galilean satellites - namely Io, Europa, Ganymede, and Callisto - is not fully understood yet. Here we use N-body numerical simulations to study the formation of Galilean satellites in a gaseous circumplanetary disk around Jupiter. Our model includes the effects of pebble accretion, gas-driven migration, and gas tidal damping and drag. Satellitesimals in our simulations first grow via pebble accretion and start to migrate inwards. When they reach the trap at the disk inner edge, scattering events and collisions take place promoting additional growth. Growing satellites event…
There is compelling evidence for subsurface water oceans among the three outer Galilean satellites, and evidence for an internal magma ocean in the innermost moon, Io. Tidal forces from Jupiter periodically deform these bodies, causing heating and deformation that, if measured, can probe their interior structures. In addition to Jupiter-raised tides, each moon also raises tides on the others. We investigate moon-moon tides for the first time in the Galilean moons, and show that they can cause significant heating through the excitation of high-frequency resonant tidal waves in their subsurface …
Electron impact ionization is critical in producing the ionospheres on many planetary bodies and, as discussed here, is critical for interpreting spacecraft and telescopic observations of the tenuous atmospheres of the icy Galilean satellites of Jupiter (Europa, Ganymede, and Callisto), which form an interesting planetary system. Fortunately, laboratory measurements, extrapolated by theoretical models, were developed and published over a number of years by K. Becker and colleagues (see Deutsch et al. 2009) to provide accurate electron impact ionization cross sections for atoms and molecules, w…
For terrestrial exoplanets with thin atmospheres or no atmospheres, the surface contributes light to the reflected light signal of the planet. Measurement of the variety of disk-integrated brightnesses of bodies in the Solar System and the variation with illumination and wavelength is essential for both planning imaging observations of directly imaged exoplanets and interpreting the eventual datasets. Here we measure the change in brightness of the Galilean satellites as a function of planetocentric longitude, illumination phase angle, and wavelength. The data span a range of wavelengths from …
Formation and Survival of Complex Organic Molecules in the Jovian Circumplanetary Disk
Southwest Research Institute（西南研究所）；Groupe de Spectrométrie Moléculaire et Atmosphérique (GSMA), Université de Reims Champagne-Ardenne, CNRS（分子与大气光谱学小组（GSMA），兰斯香槟-阿登大学，法国国家科学研究中心）；Aix-Marseille Université, CNRS, CNES, Institut Origines, LAM（艾克斯-马赛大学，法国国家科学研究中心，法国国家空间研究中心，起源研究所，天体物理与天体化学实验室）；Astronomy & Astrophysics Section, School of Cosmic Physics, Dublin Institute for Advanced Studies（都柏林高等研究院宇宙物理学院天文与天体物理系）
We investigate whether the regular Galilean satellites could have formed in the dead zone of a circumplanetary disc. A dead zone is a region of weak turbulence in which the magnetorotational instability (MRI) is suppressed, potentially an ideal environment for satellite formation. With the grid-based hydrodynamic code, FARGO3D, we examine the evolution of a circumplanetary disc model with a dead zone. Material accumulates in the dead zone of the disc leading to a higher total mass and but a similar temperature profile compared to a fully turbulent disc model. The tidal torque increases the rat…
Radar observations of Europa in 2011-2024: New insights into radar scattering properties
University of California, Los Angeles（加州大学洛杉矶分校）；EUMETSAT（欧洲气象卫星组织）；National Radio Astronomy Observatory（国家射电天文台）；Jet Propulsion Laboratory, California Institute of Technology（加利福尼亚理工学院喷气推进实验室）；University of Michigan（密歇根大学）
A stellar occultation occurs when a Solar System object passes in front of a star for an observer. This technique allows the determination of sizes and shapes of the occulting body with kilometer precision. Also, this technique constrains the occulting body's positions, albedos, densities, etc. In the context of the Galilean moons, these events can provide their best ground-based astrometry, with uncertainties in the order of 1 mas ($\sim$ 3 km at Jupiter's distance during opposition). We organized campaigns and successfully observed a stellar occultation by Io (JI) in 2021, one by Ganymede (J…
We generalize the Laplace resonance among three satellites, S1, S2 , and S3, by considering different ratios of the mean-longitude variations. These resonances, which we call Laplace-like, are classified as first order in the cases of the 2:1&2:1, 3:2&3:2, and 2:1&3:2 resonances, second order in the case of the 3:1&3:1 resonance, and mixed order in the case of the 2:1&3:1 resonance. We consider a model that includes the gravitational interaction with the central body together with the effect due to its oblateness, the mutual gravitational influence of the satellites S1, S2, and S3 and the secu…
