Formation of asteroids and meteoroids (question)
micha...@aol.com
do they get that way in the cold and low pressures of interplanetary
space. The documentaries i have seen on various science channels all
seem to indicate that small bodies are intially formed through
electrostatic forces. Even if you consider the effects of vacuum
welding, I find it hard to believe you could build anything as solid
and compact as a rock with just electrostatic accretion. My intuition
is that electrostatic accreation, random collisions and vacuum welding
would produce a low density, porous, dendritic sort of structure.
All the meteorites I have seen have been quite comapct and solid,
though I suppose that there there is a selection process for those
properties as meteors plunge through the atmosphere.
So I see four possibilities:
1) Somehow, electrostatic accreation and vacuum welding can produce
compact, strong rock-like meteoroids and asteroids, against my
physical intuition.
2) There is some other extraplanatary process responsible for making
asteroids and meteroids that can make them rock-like.
3) Asteroids and meteoroids were at one point made in some planatary
process and later ejected into space.
4) The vast majority of meteoroids and asteroids are fluffy
structures, but we only see a tiny minority of the most compact ones
on the ground that have had all their fluffiness burned away.
Of course these four possibilities are not mutually exclusive.
Phillip Helbig---remove CLOTHES to reply
"micha...@aol.com" <micha...@aol.com> writes:
> 3) Asteroids and meteoroids were at one point made in some planatary
> process and later ejected into space.
Right. Note that one can find meteorites on Earth which originate from
Mars. In the early solar system, after a critical mass was reached,
gravity was responsible for accretion of bodies. As you point out, this
can lead to a higher density. But due to later collisions (see the
craters on the moon and other bodies for evidence of impact by rather
large masses), some of these bodies were busted up into smaller pieces.
Of course, there is also a selection effect since a meteorite, by
definition, is something which has survived passage through the
atmosphere. That can't be the case with fluffy stuff.
Richard Saam
> So I see four possibilities:
>
> 1) Somehow, electrostatic accreation and vacuum welding can produce
> compact, strong rock-like meteoroids and asteroids, against my
> physical intuition.
>
> 2) There is some other extraplanatary process responsible for making
> asteroids and meteroids that can make them rock-like.
>
> 3) Asteroids and meteoroids were at one point made in some planatary
> process and later ejected into space.
>
> 4) The vast majority of meteoroids and asteroids are fluffy
> structures, but we only see a tiny minority of the most compact ones
> on the ground that have had all their fluffiness burned away.
>
> Of course these four possibilities are not mutually exclusive.
A correlation is noted that the asteroid belt
is generally in the location
of where the Pioneer deceleration anomaly commences.
The present asteroid belt location (with unaccreted objects)
has been generally explained in terms of gravitational perturbations
by Jupiter imparting too much orbital energy to the bodies in this region
for them to accrete into a planet through collisions.
Richard