97 research outputs found
Orbital Perturbations of the Galilean Satellites During Planetary Encounters
The Nice model of the dynamical instability and migration of the giant
planets can explain many properties of the present Solar System, and can be
used to constrain its early architecture. In the jumping-Jupiter version of the
Nice model, required from the terrestrial planet constraint and dynamical
structure of the asteroid belt, Jupiter has encounters with an ice giant. Here
we study the survival of the Galilean satellites in the jumping-Jupiter model.
This is an important concern because the ice-giant encounters, if deep enough,
could dynamically perturb the orbits of the Galilean satellites, and lead to
implausible results. We performed numerical integrations where we tracked the
effect of planetary encounters on the Galilean moons. We considered three
instability cases from Nesvorny & Morbidelli (2012) that differed in the number
and distribution of encounters. We found that in one case, where the number of
close encounters was relatively small, the Galilean satellite orbits were not
significantly affected. In the other two, the orbital eccentricities of all
moons were excited by encounters, Callisto's semimajor axis changed, and, in a
large fraction of trials, the Laplace resonance of the inner three moons was
disrupted. The subsequent evolution by tides damps eccentricities and can
recapture the moons in the Laplace resonance. A more important constraint is
represented by the orbital inclinations of the moons, which can be excited
during the encounters and not appreciably damped by tides. We find that one
instability case taken from Nesvorny & Morbidelli (2012) clearly fails this
constraint. This shows how the regular satellites of Jupiter can be used to set
limits on the properties of encounters in the jumping-Jupiter model, and help
us to better understand how the early Solar System evolved.Comment: The Astronomical Journal, in pres
O instituto da averbação premonitória e sua aplicabilidade ao rito da execução fiscal à luz das garantias processuais do executado
It introduces the amendments made by Law 11382, 2006, in the Code of Civil Procedure – CPC/1973 – and incorporated by the New Code of Civil Procedure, which are applicable in the tax execution procedure. It talks about the history, classification, concept and foundation of tax execution, as well as the applicability of CPC clauses to Tax Execution Laws. It analyses the institution of premonitory registration, as well as its appropriateness in the procedure set by Law 6830/1980 in light of the debtor’s procedure guarantees during a tax execution.Apresenta as alterações feitas pela Lei nº 11.382, de 2006, no Código do Processo Civil – CPC/1973 – e incorporadas pelo Novo Código de Processo Civil que são aplicáveis ao processo da execução fiscal. Trata da história, da classificação, do conceito e da fundamentação da execução fiscal, bem como da aplicabilidade das disposições do Código Processual Civil à Lei de Execuções Fiscais. Analisa o instituto da averbação premonitória, assim como o seu cabimento no processo traçado pela Lei nº 6.830/1980 à luz das garantias processuais do executado em execução fiscal
Linking planetary embryo formation to planetesimal formation I: The impact of the planetesimal surface density in the terrestrial planet zone
The growth time scales of planetary embryos and their formation process are
imperative for our understanding on how planetary systems form and develop.
They determine the subsequent growth mechanisms during the life stages of a
circumstellar disk. We quantify the timescales and spatial distribution of
planetary embryos via collisional growth and fragmentation of dynamically
forming 100km sized planetesimals. In our study, the formation timescales of
viscous disk evolution and planetesimal formation are linked to the formation
of planetary embryos in the terrestrial planet zone. We connect a one
dimensional model for viscous gas evolution, dust and pebble dynamics and
pebble flux regulated planetesimal formation to the N-body code LIPAD. Our
framework enables us to study the formation, growth, fragmentation and
evolution of planetesimals with an initial size of 100km in diameter for the
first million years of a viscous disk. Our study shows the effect of the
planetesimal surface density evolution on the preferential location and
timescales of planetary embryo formation. A one dimensional analytically
derived model for embryo formation based on the local planetesimal surface
density evolution is presented. This model manages to reproduce the spatial
distribution, formation rate and total number of planetary embryos at a
fraction of the computational cost of the N-body simulations. The formation of
planetary embryos in the terrestrial planet zone occurs simultaneously to the
formation of planetesimals. The local planetesimal surface density evolution
and the orbital spacing of planetary embryos in the oligarchic regime serve
well as constraints to model planetary embryo formation analytically. Our
embryo formation model will be a valuable asset in future studies regarding
planet formation
Linking planetary embryo formation to planetesimal formation II: The impact of pebble accretion in the terrestrial planet zone
The accretion of pebbles on planetary cores has been widely studied in recent
years and is found to be a highly effective mechanism for planetary growth.
While most studies assume planetary cores as an initial condition in their
simulation, the question how, where and when these cores form is often
neglected. We study the impact of pebble accretion during the formation phase
and subsequent evolution of planetary embryos in the early stages of
circumstellar disk evolution. In doing so we aim to quantify the timescales and
local dependency of planetary embryo formation, based on the solid evolution of
the disk. We connect a one dimensional two population model for solid evolution
and pebble flux regulated planetesimal formation to the N-body code LIPAD. In
our study we focus on the growth of planetesimals with an initial size of 100
km in diameter by planetesimal collisions and pebble accretion for the first 1
million years of a viscously evolving disk. We compare 18 different N-body
simulations in which we vary the total planetesimal mass after 1 million years,
the surface density profile of the planetesimal disk, the radial pebble flux
and the possibility of pebble accretion. Pebble accretion leads to the
formation of fewer, but substantially more massive embryos. The area of
possible embryo formation is weakly influenced by the accretion of pebbles and
the innermost embryos tend to form slightly earlier compared to the simulations
in which pebble accretion is neglected. Pebble accretion strongly enhances the
formation of super earths in the terrestrial planet region, but it does not
enhance the formation of embryos at larger distances
Isotopic Trichotomy of Main Belt Asteroids from Implantation of Outer Solar System Planetesimals
Recent analyses of samples from asteroid (162173) Ryugu returned by JAXA's
Hayabusa2 mission suggest that Ryugu and CI chondrites formed in the same
region of the protoplanetary disk, in a reservoir that was isolated from the
source regions of other carbonaceous (C-type) asteroids. Here we conduct
-body simulations in which CI planetesimals are assumed to have formed in
the Uranus/Neptune zone at --25 au from the Sun. We show that CI
planetesimals are scattered by giant planets toward the asteroid belt where
their orbits can be circularized by aerodynamic gas drag. We find that the
dynamical implantation of CI asteroids from --25 au is very efficient
with \% of -km planetesimals reaching stable orbits in the
asteroid belt by the end of the protoplanetary gas disk lifetime. The
efficiency is reduced when planetesimal ablation is accounted for. The
implanted population subsequently evolved by collisions and was depleted by
dynamical instabilities. The model can explain why CIs are isotopically
distinct from other C-type asteroids which presumably formed at --10 au.Comment: EPSL, in pres
Implications of Jupiter Inward Gas-Driven Migration for the Inner Solar System
The migration history of Jupiter in the sun's natal disk remains poorly
constrained. Here we consider how Jupiter's migration affects small-body
reservoirs and how this constrains its original orbital distance from the Sun.
We study the implications of large-scale and inward radial migration of Jupiter
for the inner solar system while considering the effects of collisional
evolution of planetesimals. We use analytical prescriptions to simulate the
growth and migration of Jupiter in the gas disk. We assume the existence of a
planetesimal disk inside Jupiter's initial orbit. This planetesimal disk
received an initial total mass and size-frequency distribution (SFD).
Planetesimals feel the effects of aerodynamic gas drag and collide with one
another, mostly while shepherded by the migrating Jupiter. Our main goal is to
measure the amount of mass in planetesimals implanted into the main asteroid
belt (MAB) and the SFD of the implanted population. We also monitor the amount
of dust produced during planetesimal collisions. We find that the SFD of the
planetesimal population implanted into the MAB tends to resemble that of the
original planetesimal population interior to Jupiter. We also find that unless
very little or no mass existed between 5 au and Jupiter's original orbit, it
would be difficult to reconcile the current low mass of the MAB with the
possibility that Jupiter migrated from distances beyond 15 au. This is because
the fraction of the original disk mass that gets implanted into the MAB is very
large. Finally, we discuss the implications of our results in terms of dust
production to the so-called NC-CC isotopic dichotomy.Comment: Accepted for publication in The Astrophysical Journal Letters; In
pres
A race against the clock: Constraining the timing of cometary bombardment relative to Earth's growth
Comets are considered a potential source of inner solar system volatiles, but
the timing of this delivery relative to that of Earth's accretion is still
poorly understood. Measurements of xenon isotopes in comet
67P/Churyumov-Gerasimenko revealed that comets partly contributed to the
Earth's atmosphere. However, there is no conclusive evidence of a significant
cometary component in the Earth's mantle. These geochemical constraints would
favour a contribution of comets mainly occurring after the last stages of
Earth's formation. Here, we evaluate whether dynamical simulations satisfy
these constraints in the context of an Early Instability model. We perform
dynamical simulations of the solar system, calculate the probability of
collision between comets and Earth analogs component embryos through time and
estimate the total cometary mass accreted in Earth analogs as a function of
time. While our results are in excellent agreement with geochemical
constraints, we also demonstrate that the contribution of comets on Earth might
have been delayed with respect to the timing of the instability, due to a
stochastic component of the bombardment. More importantly, we show that it is
possible that enough cometary mass has been brought to Earth after it had
finished forming so that the xenon constraint is not necessarily in conflict
with an Early Instability scenario. However, it appears very likely that a few
comets were delivered to Earth early in its accretion history, thus
contributing to the mantle's budget. Finally, we compare the delivery of
cometary material on Earth to Venus and Mars. These results emphasize the
stochastic nature of the cometary bombardment in the inner solar system.Comment: 26 pages, 12 figure
Identification of a 4.3 billion year old asteroid family and planetesimal population in the Inner Main Belt
After performing a reassessment of the known dynamical asteroid families in
the inner main belt, we report a newly discovered ancient asteroid family with
an estimated age of billion years. Additionally, we report the most
comprehensive list of planetesimals, which are asteroids that survived since
the planet forming days of the solar system.Comment: 21 pages, 13 figure
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