Was it a planet, originally?
One that broke up?
One of the stronger theories about the evolution of our solar system proposes there there may have been as many as 100 “proto-planetoidss” orbiting an evolving Sol (our Sun’s name). Over eons of time they progressively dwindled away due to collisions in a chaotic process of destruction and rebirth, as the fragments clumped together again and again in ever growing masses. The asteriod belt is thought to be a remnant of what was left over.
But, as the Shoemaker-Levy comet impact Jupiter reminded us, the process isn’t finished yet…
The BBC series “The Planets” has a really good discussion of this theory pitched perfectly at the layman level. I highly recommend it to get a better idea of the big picture.
It’s either one that never formed, or one that broke up. No one knows for sure.
But then again, what is a “planet” anyway? If you’re thinking of a Sun-orbiting body of a certain size, you should know that all the mass of all the asteroids in the Belt put together would be less than that of Earth’s Moon.
So all that material never would have amounted to much even if it had coalesced (but don’t tell its mother!).
Well, there’s Bode’s law:
This, of course, doesn’t say anything about Jupiter, but I always thought it was interesting. I really don’t know much about this stuff, but as I understand, Bode’s law is generally thought of as somewhat interesting, but in large part just a coincidence.
Anyway, my point is that the asteroid belt does fall into a nice pattern with the other planets. As far as I know, the common theory is that each of the planets begin as debris that clumped together over time, aided by larger and larger gravitational pulls of larger and larger clumps. Jupiter’s gravitational pull, because Jupiter is such a big planet, and because it’s so relatively close to the asteroid belt, provided enough “chaotic distortion”, I suppose, to disallow “big enough” clumps from ever forming in the asteroid belt, preventing a full blown planet from ever forming. I know there are some astronomers out there, so please correct any of this if necessary.
I meant that to say asteroid belt (and how it came to be there), not Jupiter.