647 research outputs found
Collision probabilities of migrating small bodies and dust particles with planets
Probabilities of collisions of migrating small bodies and dust particles
produced by these bodies with planets were studied. Various Jupiter-family
comets, Halley-type comets, long-period comets, trans-Neptunian objects, and
asteroids were considered. The total probability of collisions of any
considered body or particle with all planets did not exceed 0.2. The amount of
water delivered from outside of Jupiter's orbit to the Earth during the
formation of the giant planets could exceed the amount of water in Earth's
oceans. The ratio of the mass of water delivered to a planet by Jupiter-family
comets or Halley-type comets to the mass of the planet can be greater for Mars,
Venus, and Mercury, than that for Earth.Comment: 7 pages (original paper consists of 4 pages, with all sub-figures on
one page). Proceedings of the IAU Symposium 263 "Icy bodies in the Solar
System" (Rio de Janeiro, Brazil, 3-7 August, 2009), ed. by D. Lazzaro, D.
Prialnik, R. Schulz, J.A. Fernandez, submitte
Migration of Jupiter-family comets and resonant asteroids to near-Earth space
We estimated the rate of comet and asteroid collisions with the terrestrial
planets by calculating the orbits of 13000 Jupiter-crossing objects (JCOs) and
1300 resonant asteroids and computing the probabilities of collisions based on
random-phase approximations and the orbital elements sampled with a 500 yr
step. The Bulirsh-Stoer and a symplectic orbit integrator gave similar results
for orbital evolution, but sometimes give different collision probabilities
with the Sun. A small fraction of former JCOs reached orbits with aphelia
inside Jupiter's orbit, and some reached Apollo orbits with semi-major axes
less than 2 AU, Aten orbits, and inner-Earth orbits (with aphelia less than
0.983 AU) and remained there for millions of years. Though less than 0.1% of
the total, these objects were responsible for most of the collision probability
of former JCOs with Earth and Venus. Some Jupiter-family comets can reach
inclinations i>90 deg. We conclude that a significant fraction of near-Earth
objects could be extinct comets that came from the trans-Neptunian region.Comment: Proc. of the international conference "New trends in astrodynamics
and applications" (20-22 January 2003, University of Maryland, College Park
The angular momentum of two collided rarefied preplanetesimals and the formation of binaries
This paper studies the mean angular momentum associated with the collision of
two celestial objects in the earliest stages of planet formation. Of primary
concern is the scenario of two rarefied preplanetesimals (RPPs) in circular
heliocentric orbits. The theoretical results are used to develop models of
binary or multiple system formation from RPPs, and explain the observation that
a greater fraction of binaries originated farther from the Sun. At the stage of
RPPs, small-body satellites can form in two ways: a merger between RPPs can
have two centers of contraction, or the formation of satellites from a disc
around the primary or the secondary. Formation of the disc can be caused by
that the angular momentum of the RPP formed by the merger is greater than the
critical angular momentum for a solid body. One or several satellites of the
primary (moving mainly in low-eccentricity orbits) can be formed from this disc
at any separation less than the Hill radius. The first scenario can explain a
system such as 2001 QW322 where the two components have similar masses but are
separated by a great distance. In general, any values for the eccentricity and
inclination of the mutual orbit are possible. Among discovered binaries, the
observed angular momenta are smaller than the typical angular momenta expected
for identical RPPs having the same total mass as the discovered binary and
encountering each other in circular heliocentric orbits. This suggests that the
population of RPPs underwent some contraction before mergers became common.Comment: 12 pages, Monthly Notices of Royal Astron. Society, in pres
Comet and Asteroid Hazard to the Terrestrial Planets
We estimated the rate of comet and asteroid collisions with the terrestrial
planets by calculating the orbits of 13000 Jupiter-crossing objects (JCOs) and
1300 resonant asteroids and computing the probabilities of collisions based on
random-phase approximations and the orbital elements sampled with a 500 yr
step. The Bulirsh-Stoer and a symplectic orbit integrator gave similar results
for orbital evolution, but may give different collision probabilities with the
Sun. A small fraction of former JCOs reached orbits with aphelia inside
Jupiter's orbit, and some reached Apollo orbits with semi-major axes less than
2 AU, Aten orbits, and inner-Earth orbits (with aphelia less than 0.983 AU) and
remained there for millions of years. Though less than 0.1% of the total, these
objects were responsible for most of the collision probability of former JCOs
with Earth and Venus. We conclude that a significant fraction of near-Earth
objects could be extinct comets that came from the trans-Neptunian region.Comment: "Advances in Space Research" (Proc. of COSPAR-2002 (10-19 October
2002, Houston, TX, USA), COSPAR02-A-00845), final tex
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