10 research outputs found
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
Migration of Small Bodies and Dust to Near-Earth Space
The orbital evolution of Jupiter-family comets (JFCs), resonant asteroids,
and asteroidal, trans-Neptunian, and cometary dust particles under the
gravitational influence of planets was integrated. For dust particles we also
considered radiation pressure, Poynting-Robertson drag, and solar wind drag.
The probability of a collision of one former JFC with a terrestrial planet can
be greater than analogous total probability for thousands other JFCs. If those
former JFCs that got near-Earth object (NEO) orbits for millions of years
didn't disintegrate during this time, there could be many extinct comets among
NEOs. The maximum probability of a collision of an asteroidal or cometary dust
particle with the Earth during its lifetime was for diameter 100
microns. At 10 micron, the collision probability of a trans-Neptunian
particle with the Earth during a lifetime of the particle was less than that
for an asteroidal particle by only a factor of several.Comment: Submitted to Advances in Space Research (Proceedings of COSPAR-2004
Evolution of the orbits of the objects P/1996 R2 (Lagerkvist) and P/1996 N2 (Elst-Pizarro)
Two new interesting objects were observed recently in the asteroid belt. The object P/1996 R2 (Lagerkvist) has a Jupiter-crossing orbit. On August 7, 1996 Elst reported his discovery of the object with a tail, which looked like a comet. This object was named P/1996 N2 'Elst-Pizarro' has a typical asteroid orbit, and was identified with the object 1979 OW7