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Re: asteroid capture AND ring material escape?
Jarmo Korteniemi wrote:
>
> Hi.
>
> This planetary ring discussion brought one thing to my attention.. a
> thing which I seem to have forgotten, so would someone please clarify
> this?
>
> Is it true that any object in an orbit around the Sun (at the distance
> of for example the asteroid belt or closer to the Sun) CAN NOT be
> captured by a planet? As far as I remember, Earth's velocity around the
> Sun is about 30km/sec (for Mars 24km/sec). And the escape velocity of
> Earth is 11km/sec..
>
> Come to think of it, the planetary probes have to use propulsion or some
> other form of deceleration (aircapture etc) to reach a planetary orbit..
> There, I seem to have answered my own question. (Have I?)
>
> I guess this would go both ways then: For an Earth-orbiting chunk of
> rock, it would be needed an extra "push" to reach a heliospheric orbit?
> So, if there was a planetary ring around the Earth, how could this newly
> found asteroid OUTSIDE Earth's orbit, circling the Sun, be a remnant of
> that ring?
>
> --
> | Jarmo Korteniemi http://www.student.oulu.fi/~jkorteni/
> | student
> | Dept. of Astronomy "Science is hard. Wishful thinking is easy."
> | Oulu University -P.Stephens, The South Shore Skeptic,May'98
>
It may not necessarily be a remnant of the ring, but of the collision
that caused the ring. If it is a remnant of the ring, there may have
been collisions or a close gravitational encounter between ring particles
that could have caused a piece of the collision to be thrown out of its
orbit fast enough to escape its orbit around the Earth.
For being captured by a planet, Jupiter has 4 outer satellites that
appear to be captured asteroids. And both Phobos and Deimos also
appear to have been captured by Mars. This is much easier if the
orbit of the asteroid is close to circular. If it is too elliptical,
it velocity as it passes a planet will be too great to allow
it to be captured by that planet. This is the case for most
interplanetary space probes, which is why they are required to
be slowed down by either a rocket burn or aerobraking.
Mike
--
41.087N 80.714W 305 meters
Mike DiMuzio mdimuzio@cisnet.com
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