Main Asteroid Belt No Remnant Of Exploded Planet

[Buster's Uncle]

Main Asteroid Belt No Remnant Of Exploded Planet
Bruce Dorminey, Contributor 1/31/2013 @ 7:35PM



Artist's concept of a narrow asteroid belt potentially around another sunlike star. Credit: NASA/JPL-Caltech


For years now, there have been claims from the astronomical fringes that our solar system’s Main Asteroid Belt contains the destroyed, or even “exploded,” remains of one or more full-scale planets.

Just what could have plausibly caused such wholesale destruction — down to meter-sized rocky objects — is open for debate.

Internet forums are full of ideas — invoking everything from “matter-anti-matter” explosions to war-mongering “space aliens.”

If that’s not enough, there have even been assertions that Mars itself is actually such an exploded planet’s scattered former moon.

It’s the kind of speculative tidbit that makes for great late night radio, but it’s complete anathema to mainstream planetary science.

 Millions of rocky objects still inhabit the Main Belt ranging in size from the newly reclassified dwarf planet Ceres, which at 1000 kilometers in diameter remains the Belt’s largest known body, down to scales wholly undetectable with present technology. But even if all the Main Belt’s material were swept up to make a single body, there still wouldn’t be enough to make a full-sized terrestrial mass planet.

Thus, as Nick Moskovitz, a planetary scientist at M.I.T. and an expert on the Main Asteroid Belt, points out, the belt could have never hosted a planet large enough to claim Mars as a satellite.

Even assuming at the time of its formation that the belt was 100 times more massive than today, he says, its total mass would have been only about half that of Mars. So, the “host planet” would actually have to be smaller than its satellite.

“There’s a not a single piece of concrete evidence that would suggest that there ever was a full-sized planet in the asteroid belt,” said Moskovitz. “In the region of the Main Belt, it’s dynamically impossible in the presence of Jupiter’s gravitational influence for small bodies to collide and stick together to form a full-sized planet.”

In truth, the mass of the Main Belt — which extends just past the orbit of Mars to about three and a half times the distance from the Earth to the Sun — has not changed much over the 4.5 billion year life of the solar system.

Moskovitz says the belt that we see today is the result of a population of bodies that have spent the subsequent 4.5 billion years interacting and colliding with one another.

Although downward-looking diagrams of the Main Asteroid Belt make it look incredibly dense, the region has significant gaps, clumps and clusters. And if someone were actually on a spacecraft traveling through the region, chances are the next nearest slab of rock would be at least a few hundred thousand kilometers away.

Early on, Moskovitz says the entire solar system probably resembled one giant asteroid belt. Then as the planets formed, they cleared out the material in their vicinity.



Image of the main asteroid belt between the orbits of Mars and Jupiter. (Photo credit: Wikipedia)


However, because there’s no planet in the asteroid belt, it remains a relic dumping ground of sorts for material from all over the solar system.

But it is arguably best suited as an asteroidal Rosetta Stone in interpreting our own solar system’s evolutionary twists and turns.

Even though the Main Belt represents only a small fraction of the total extent of our solar system, as Moskovitz points out, the belt is replete with a huge diversity of geologic histories. It also continues to serve as a point of theoretical comparison with the internal dynamics of the many recently-discovered extra-solar planetary systems.



MIT Planetary Scientist Nick Moskovitz. Image courtesy of Moskovitz


Partly as a result, many planetary theorists now think that our four outer gas giant planets — Jupiter, Saturn, Uranus and Neptune — actually formed much closer together and farther in than their current orbits would indicate.

But cataclysmic gravitational interactions between Jupiter and Saturn caused these behemoths to migrate out to their present orbits.

“These rearrangements caused lots of Main Belt chaos,” said Moskovitz. “Within its first few hundred million years, the whole architecture of the solar system changed dramatically.”


http://www.forbes.com/sites/brucedorminey/2013/01/31/why-our-main-asteroid-belt-is-hardly-the-remnant-of-an-exploded-planet/

[Geo]

Goodbye, Peter F. Hogan.
But, if the outer planets supposedly migrated outwards (where many exojupiters supposedly migrated inwards btw), how about the terrestrial inner planets of our sun?

EDIT: spelling

[Buster's Uncle]

No telling.  But it seems clearer and clearer, as our observations of the universe become more complete, that given a few billion years of relative peace, all sorts of orbital resonances happen.  That probably accounts for the predictable, roughly x2, orbital radiuses.  I doubt that in the short run that effects formation locations, just where the stable orbits turn out to be.  We're talking about pretty subtle forces or it wouldn't takes billions of years.