[meteorite-list] Catch A Comet?

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Mon, 14 Sep 2009 12:00:53 -0500
Message-ID: <D6802A115C214DE2B2D9453FDE9D4825_at_ATARIENGINE2>

It seems that not only do comets impact Jupiter,
they may also become moons, temporary or
permanent, of the planet.

Wonder what it would take to get a "comet moon"
for the Earth?

Sterling K. Webb
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http://www.space.com/scienceastronomy/090914-jupiter-comet.html
Gotcha! Jupiter Turned Comet into a Moon
By SPACE.com Staff

Jupiter already has an abundance of moons,
but from 1949 to 1961 it had another, temporary
satellite in the form of a comet trapped in the
gas giant's gravitational grip.

Comet 147P/Kushida-Muramatsu was captured
as a temporary moon of Jupiter in the mid-20th
century and remained trapped in an irregular
orbit for about twelve years, astronomers announced
today.

There are only a handful of known comets where
this phenomenon of temporary satellite capture
has occurred and the capture duration in the
case of Kushida-Muramatsu is the third longest.

The discovery was presented today at the European
Planetary Science Congress in Potsdam by David
Asher of Armagh Observatory in Northern Ireland.

An international team led by Katsuhito Ohtsuka
of the Tokyo Meteor Network modeled the trajectories
of 18 "quasi-Hilda comets," objects with the potential
to go through a temporary satellite capture by
Jupiter that results in them either leaving or joining
the "Hilda" group of objects in the asteroid belt.
Most of the cases of temporary capture were flybys,
where the comets did not complete a full orbit.

But Kushida-Muramatsu was different: The team
used recent observations tracking the comet over
nine years to calculate hundreds of possible orbital
paths for it over the previous century. In all scenarios,
Kushida-Muramatsu completed two full revolutions
of Jupiter, making it only the fifth captured orbiter
to be identified.

"Our results demonstrate some of the routes taken
by cometary bodies through interplanetary space
that can allow them either to enter or to escape
situations where they are in orbit around the planet
Jupiter," Asher said.

Asteroids and comets can sometimes be distorted
or fragmented by tidal effects induced by the
gravitational field of a capturing planet, or may
even impact with the planet. The most famous
victim of both these effects was comet D/1993 F2
(Shoemaker-Levy 9), which was torn apart on
passing close to Jupiter and whose fragments
then collided with that planet in 1994. Previous
computational studies have shown that Shoemaker-Levy 9
may well have been a quasi-Hilda comet before
its capture by Jupiter.

"Fortunately for us Jupiter, as the most massive
planet with the greatest gravity, sucks objects
towards it more readily than other planets and
we expect to observe large impacts there more
often than on Earth. Comet Kushida-Muramatsu
has escaped from the giant planet and will avoid
the fate of Shoemaker-Levy 9 for the foreseeable
future," Asher said.

The object that impacted with Jupiter this July,
causing the new dark spot discovered by Australian
amateur astronomer Anthony Wesley, may also
have been a member of this class, even if it did
not suffer tidal disruption like Shoemaker-Levy.

"Our work has become very topical again with the
discovery this July of an expanding debris plume,
created by the dust from the colliding object, which
is the evident signature of an impact. The results of
our study suggest that impacts on Jupiter and
temporary satellite capture events may happen
more frequently than we previously expected,"
Asher said.

The team has also confirmed a future moon of
Jupiter. Comet 111P/Helin-Roman-Crockett,
which has already orbited Jupiter three times
between 1967 and 1985, is due to complete six
laps of the giant planet between 2068 and 2086.
Received on Mon 14 Sep 2009 01:00:53 PM PDT