20,250 research outputs found
On The Effect of Giant Planets on the Scattering of Parent Bodies of Iron Meteorite from the Terrestrial Planet Region into the Asteroid Belt: A Concept Study
In their model for the origin of the parent bodies of iron meteorites, Bottke
et al proposed differentiated planetesimals that were formed in the region of
1-2 AU during the first 1.5 Myr, as the parent bodies, and suggested that these
objects and their fragments were scattered into the asteroid belt as a result
of interactions with planetary embryos. Although viable, this model does not
include the effect of a giant planet that might have existed or been growing in
the outer regions. We present the results of a concept study where we have
examined the effect of a planetary body in the orbit of Jupiter on the early
scattering of planetesimals from terrestrial region into the asteroid belt. We
integrated the orbits of a large battery of planetesimals in a disk of
planetary embryos, and studied their evolutions for different values of the
mass of the planet. Results indicate that when the mass of the planet is
smaller than 10 Earth-masses, its effects on the interactions among
planetesimals and planetary embryos is negligible. However, when the planet
mass is between 10 and 50 Earth-masses, simulations point to a transitional
regime with ~50 Earth-mass being the value for which the perturbing effect of
the planet can no longer be ignored. Simulations also show that further
increase of the mass of the planet strongly reduces the efficiency of the
scattering of planetesimals from the terrestrial planet region into the
asteroid belt. We present the results of our simulations and discuss their
possible implications for the time of giant planet formation.Comment: 20 pages, 7 figures, accepted for publication in Ap
The evolution of the orbit distance in the double averaged restricted 3-body problem with crossing singularities
We study the long term evolution of the distance between two Keplerian
confocal trajectories in the framework of the averaged restricted 3-body
problem. The bodies may represent the Sun, a solar system planet and an
asteroid. The secular evolution of the orbital elements of the asteroid is
computed by averaging the equations of motion over the mean anomalies of the
asteroid and the planet. When an orbit crossing with the planet occurs the
averaged equations become singular. However, it is possible to define piecewise
differentiable solutions by extending the averaged vector field beyond the
singularity from both sides of the orbit crossing set. In this paper we improve
the previous results, concerning in particular the singularity extraction
technique, and show that the extended vector fields are Lipschitz-continuous.
Moreover, we consider the distance between the Keplerian trajectories of the
small body and of the planet. Apart from exceptional cases, we can select a
sign for this distance so that it becomes an analytic map of the orbital
elements near to crossing configurations. We prove that the evolution of the
'signed' distance along the averaged vector field is more regular than that of
the elements in a neighborhood of crossing times. A comparison between averaged
and non-averaged evolutions and an application of these results are shown using
orbits of near-Earth asteroids.Comment: 29 pages, 8 figure
Terrestrial Planet Formation Constrained by Mars and the Structure of the Asteroid Belt
Reproducing the large Earth/Mars mass ratio requires a strong mass depletion
in solids within the protoplanetary disk between 1 and 3 AU. The Grand Tack
model invokes a specific migration history of the giant planets to remove most
of the mass initially beyond 1 AU and to dynamically excite the asteroid belt.
However, one could also invoke a steep density gradient created by inward drift
and pile-up of small particles induced by gas-drag, as has been proposed to
explain the formation of close-in super Earths. Here we show that the asteroid
belt's orbital excitation provides a crucial constraint against this scenario
for the Solar System. We performed a series of simulations of terrestrial
planet formation and asteroid belt evolution starting from disks of
planetesimals and planetary embryos with various radial density gradients and
including Jupiter and Saturn on nearly circular and coplanar orbits. Disks with
shallow density gradients reproduce the dynamical excitation of the asteroid
belt by gravitational self-stirring but form Mars analogs significantly more
massive than the real planet. In contrast, a disk with a surface density
gradient proportional to reproduces the Earth/Mars mass ratio but
leaves the asteroid belt in a dynamical state that is far colder than the real
belt. We conclude that no disk profile can simultaneously explain the structure
of the terrestrial planets and asteroid belt. The asteroid belt must have been
depleted and dynamically excited by a different mechanism such as, for
instance, in the Grand Tack scenario.Comment: Accepted for publication in MNRA
Studies of asteroids, comets, and Jupiter's outer satellites
Observational, theoretical, and computational research was performed, mainly on asteroids. Two principal areas of research, centering on astrometry and photometry, are interrelated in their aim to study the overall structure of the asteroid belt and the physical and orbital properties of individual asteroids. Two highlights are: detection of CN emission from Chiron; and realization that 1990 MB is the first known Trojan type asteroid of a planet other than Jupiter. A new method of asteroid orbital error analysis, based on Bayesian theory, was developed
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