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Re: Stimulating questions

Hello jj,

It seems we just can't get you away from the Planet-X theory.  :-)

There are a couple of basic principles you should keep in mind. Building
on my previous post concerning chondritic material from Mercury and
Venus, if a planet had formed where the asteroid belt is, it would have
differentiated as the larger asteroids like Ceres, Pallas and Vesta
have. Since most of our stone meteorites are chondritic and have spectra
close to the majority of asteroids, most theories accept that most stone
asteroids are chondritic and could never have been part of a
differentiated body.

Second, Jupiter is not the size it is because it formed second, third or
fifth in the sequence of planets. Many, if not all the planets, formed
simultaneously within a few tens of millions of years (if that) and the
proto-Jupiter was a large mass to be reckoned with early in planetary
formation. It is possibly a fluke of mass distribution and availability
that kept Jupiter from becoming a second sun.

Third, the asteroid belt is not the only asteroid belt. It is, after
all, referred to as the main asteroid belt. Minor belts include the Aten
asteroids, inside Earth's orbit, the Earth crossing Apollos and the
Amors the come close to the outside of Earth's orbit. Further out is the
Kuiper Belt starting around Neptune's orbit and thought to go out to at
least 30 AU. There are also the Centaur objects between Jupiter and
Neptune that may be runaways from the Kuiper Belt. Centaurs and Kuiper
objects are more cometary than asteroidal, but that is a function of
available material rather than formation process.

For some interesting reading, you might want to go through the SEDS Nine
Planets site at
http://www.seds.org/nineplanets/nineplanets/nineplanets.html or read Hap
McSween's new book, Fanfare for Earth. The first half gives a quite
in-depth review of the history of solar system formation models and the
most current model (and it's very easy reading considering the subject
matter).

Gene
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