15 research outputs found
Signatures of massive collisions in debris discs
Violent stochastic collisional events have been invoked as a possible
explanation for some debris discs displaying pronounced asymmetries or having a
great luminosity excess. So far, no thorough modelling of the consequences of
such events has been carried out, mainly because of the extreme numerical
challenge of coupling the dynamical and collisional evolution of dust.
We perform the first fully self-consistent modelling of the aftermath of
massive breakups in debris discs. We follow the collisional and dynamical
evolution of dust released after the breakup of a Ceres-sized body at 6 AU from
its central star. We investigate the duration, magnitude and spatial structure
of the signature left by such a violent event, as well as its observational
detectability.
We use the recently developed LIDT-DD code (Kral et al., 2013), which handles
the coupled collisional and dynamical evolution of debris discs. The main focus
is placed on the complex interplay between destructive collisions, Keplerian
dynamics and radiation pressure forces. We use the GRaTer package to estimate
the system's luminosity at different wavelengths.
The breakup of a Ceres-sized body at 6 AU creates an asymmetric dust disc
that is homogenized, by the coupled action of collisions and dynamics, on a
timescale of a few years. The luminosity excess in the breakup's
aftermath should be detectable by mid-IR photometry, from a 30 pc distance,
over a period of years that exceeds the duration of the asymmetric
phase of the disc (a few years). As for the asymmetric structures, we
derive synthetic images for the SPHERE/VLT and MIRI/JWST instruments, showing
that they should be clearly visible and resolved from a 10 pc distance. Images
at 1.6m (marginally), 11.4 and 15.5m would show the inner disc
structures while 23m images would display the outer disc asymmetries.Comment: 16 pages, 14 figures, abstract shortened, accepted for publication in
A&
3D Lagrangian turbulent diffusion of dust grains in a protoplanetary disk: method and first applications
In order to understand how the chemical and isotopic compositions of dust
grains in a gaseous turbulent protoplanetary disk are altered during their
journey in the disk, it is important to determine their individual
trajectories. We study here the dust-diffusive transport using lagrangian
numerical simulations using the the popular "turbulent diffusion" formalism.
However it is naturally expressed in an Eulerian form, which does not allow the
trajectories of individual particles to be studied. We present a simple
stochastic and physically justified procedure for modeling turbulent diffusion
in a Lagrangian form that overcomes these difficulties. We show that a net
diffusive flux F of the dust appears and that it is proportional to the gas
density ({\rho}) gradient and the dust diffusion coefficient Dd:
(F=Dd/{\rho}\timesgrad({\rho})). It induces an inward transport of dust in the
disk's midplane, while favoring outward transport in the disk's upper layers.
We present tests and applications comparing dust diffusion in the midplane and
upper layers as well as sample trajectories of particles with different sizes.
We also discuss potential applications for cosmochemistry and SPH codes.Comment: Accepted for publication in ApJ, 37 pages, 12 Figure
Exploring the recycling model of Phobos formation: rubble-pile satellites
Phobos is the target of the return sample mission Martian Moons eXploration
by JAXA that will analyze in great details the physical and compositional
properties of the satellite from orbit, from the surface and in terrestrial
laboratories, giving clues about its formation. Some models propose that Phobos
and Deimos were formed after a giant impact giving rise to an extended debris
disk. Assuming that Phobos formed from a cascade of disruptions and
re-accretions of several parent bodies in this disk, and that they are all
characterized by a low material cohesion, Hesselbrock & Milton (2017) have
showed that a recycling process may happen during the assembling of Phobos, by
which Phobos' parents are destroyed into a Roche-interior ring and reaccreted
several times. In the current paper we explore in details the recycling model,
and pay particular attention to the characteristics of the disk using 1D models
of disk/satellite interactions. In agreement with previous studies we confirm
that, if Phobos' parents bodies are gravitational aggregates (rubble piles),
then the recycling process does occur. However, Phobos should be accompanied
today by a Roche-interior ring. Furthermore, the characteristics of the ring
are not reconcilable with today`s observations of Mars' environment, which put
stringent constraints on the existence of a ring around Mars. The recycling
mechanism may or may not have occurred at the Roche limit for an old moon
population, depending on their internal cohesion. However, the Phobos we see
today cannot be the outcome of such a recycling process.Comment: Accept in The Astronomical Journa
Deciphering the Origin of the Regular Satellites of Gaseous Giants - Iapetus: the Rosetta Ice-Moon
Here we show that Iapetus can serve to discriminate between satellite
formation models. Its accretion history can be understood in terms of a
two-component gaseous subnebula, with a relatively dense inner region, and an
extended tail out to the location of the irregular satellites, as in the SEMM
model of Mosqueira and Estrada (2003a,b). Following giant planet formation,
planetesimals in the feeding zone of Jupiter and Saturn become dynamically
excited, and undergo a collisional cascade. Ablation and capture of
planetesimal fragments crossing the gaseous circumplanetary disks delivers
enough collisional rubble to account for the mass budgets of the regular
satellites of Jupiter and Saturn. This process can result in rock/ice
fractionation provided the make up of the population of disk crossers is
non-homogeneous, thus offering a natural explanation for the marked
compositional differences between outer solar nebula objects and those that
accreted in the subnebulae of the giant planets. Consequently, our model leads
to an enhancement of the ice content of Iapetus, and to a lesser degree those
of Ganymede, Titan and Callisto, and accounts for the (non-stochastic)
compositions of these large, low-porosity outer regular satellites of Jupiter
and Saturn. (abridged)Comment: 33 pages, 7 figures, 2 tables, Accepted for publication to Icaru
New Frontiers-class Uranus Orbiter: Exploring the feasibility of achieving multidisciplinary science with a mid-scale mission
n/
Revisiting Dimorphos formation: A pyramidal regime perspective and application to Dinkinesh’s satellite
International audienc
How Mimas cleared the Cassini Division
International audienceRecent measurements of the dissipation of Saturn (Lainey et al. 2016, Icarus, in press) combined with a theoretical study by Fuller et al. (2016, MNRAS) require to revisit the energy dissipation models in planetary systems and the way it affects their satellite system. In addition, the measurements of the large librations of Mimas (Tajeddine et al. 2014, Science) could point to a global ocean underneath the surface of the satellite. These results allowed us to refine the scenarios of the opening of the Cassini Division that we initially presented at the DPS 2012. Assuming a dissipation that is consistent with these latest results, we propose scenarios of combined evolutions of Mimas and the main rings of Saturn, that explain the current size and location of the Division, the excess of density in the outer B ring, a past episode of intense heating of Mimas required to create a global ocean, and its current eccentricity. For that, we show that a past resonance with Tethys increased the eccentricity of Mimas up to 0.2, possibly triggering the melting of Mimas and an episode of inward migration, which created the Cassini Division: the 2:1 resonance between Mimas and the rings pushed the ring material inner to accumulate in the B ring. Once its eccentricity is damped, Mimas resumes its outward migration, leading to a trapping into the current vertical resonance with Tethys. These results are supported by numerical simulations, in which Mimas is driven by the tides, and the rings are simulated with the 1-D hydrodynamical code Hydrorings (Charnoz et al., 2010, Nature). This study has been partially supported by the International Space Sciences Institute in Bern, Switzerland
How Mimas cleared the Cassini Division
International audienceRecent measurements of the dissipation of Saturn (Lainey et al. 2016, Icarus, in press) combined with a theoretical study by Fuller et al. (2016, MNRAS) require to revisit the energy dissipation models in planetary systems and the way it affects their satellite system. In addition, the measurements of the large librations of Mimas (Tajeddine et al. 2014, Science) could point to a global ocean underneath the surface of the satellite. These results allowed us to refine the scenarios of the opening of the Cassini Division that we initially presented at the DPS 2012. Assuming a dissipation that is consistent with these latest results, we propose scenarios of combined evolutions of Mimas and the main rings of Saturn, that explain the current size and location of the Division, the excess of density in the outer B ring, a past episode of intense heating of Mimas required to create a global ocean, and its current eccentricity. For that, we show that a past resonance with Tethys increased the eccentricity of Mimas up to 0.2, possibly triggering the melting of Mimas and an episode of inward migration, which created the Cassini Division: the 2:1 resonance between Mimas and the rings pushed the ring material inner to accumulate in the B ring. Once its eccentricity is damped, Mimas resumes its outward migration, leading to a trapping into the current vertical resonance with Tethys. These results are supported by numerical simulations, in which Mimas is driven by the tides, and the rings are simulated with the 1-D hydrodynamical code Hydrorings (Charnoz et al., 2010, Nature). This study has been partially supported by the International Space Sciences Institute in Bern, Switzerland
Long-term dust dynamics in Didymos and Dimorphos system: Production, stability, and transport
International audienceTarget of NASA's DART mission, the system of Didymos and Dimorphos will once again be visited by a space mission-ESA's Hera mission, scheduled to be launch in 2024. Hera will arrive in the system approximately 4 years after the DART impact, a long period compared to Dimorphos' orbital period (≃ 12 h). It is therefore imperative to understand the dynamics of material in this environment on a long timescale. Here, we explore the long-term dynamics of the binary system (65038) Didymos, in the context of the perturbed, planar, circular and restricted 3-body problem. We design an analytical description for a symmetrical top-shaped object, the shape assumed for the Didymos, while the Dimorphos is considered an ellipsoid. In the absence of external effects, we identify seven stable equatorial regions where particles persist for more than a decade. However, in the presence of the solar radiation effect, the lifetime of small particles (≲ mm) is in the order of days, being unlikely that Hera spacecraft will encounter clusters of millimeter and sub-millimeter particles in stable equatorial orbits. Nonetheless, large objects may reside in the region for some years, particularly in quasisatellite orbits, the most stable orbits in the system. Additionally, interplanetary dust impacts onto Didymos populate the region, extending up to a distance of approximately 1500 m from the primary center, with young dust. These impacts are responsible for a transfer of dust mainly from Didymos to Dimorphos. If the interplanetary dust impacts generate metric-sized boulders, they may persist in the system for years, in first sort orbits around Didymos