the asteroid belt

[damienpaul]

Okay, silly question time...is there any chance that the asteroid belt could have been a planet and what size would have it been?

[Littlemews]

Is there any chance that the asteroid belt could have been a planet

Yes, that's why we sometimes called it "Minor Planets" because they are similiar to planets, but smaller

What size would have it been?

Like Deimos and Phobos (Mars's Moon)

[rajasun]

I suggest both of you look at the following papers, abstracts and articles on the LATEST coming out of research (applying sophisticated N-body simulation algorithmns, etc).

Briefly, there are 3 different views i.e.

1.) There was NEVER EVER enough mass in the primodial Main Asteroid Belt necessary for ANY major accretional effort. Moreover, the initially eccentric Jupiter and Saturn would have put paid to any nascent planet construction activity there.

NOW for the 2 CONTROVERSIAL hypotheses...

1.)
Chambers, Wetherill and Morbidelli have proposed that there WAS a FIFTH terrestrial planet whom they call "Planet V". Planet V, they believed was originally on a low eccentricity orbit that after a timeframe of ~0.1 Gyrs or so of chaotic perturbations by other inner terrestrial planets became a planet crossing one. Planet V was said to have been responsible for the LATE Heavy Bombardment and perhaps the formation of the moon itself. Ultimately Planet V was flung into the Sun.

Links to
John E. Chambers et al's hypothesis and research:
a.)
http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1093.pdf
Chambers, J. E., & Lissauer, J.J., "A New Dynamical Model for the Late Heavy Bombardment", 33rd Annual LPSC, March 11-15, 2002, Houston, Texas, abstract no.1093

b.)
Chambers, J. E., & Wetherill, G. W., 2001, "Planets in the asteroid belt", Meteoritics & Planetary Science, 36, p. 381-399

Abstract
The main asteroid belt has lost >99.9% of its solid mass since the time at which the planets were forming, according to models for the protoplanetary nebula. Here we show that the primordial asteroid belt could have been cleared efficiently if much of the original mass accreted to form planet-sized bodies, which were capable of perturbing one another into unstable orbits. We provide results from 25 N-body integrations of up to 200 planets in the asteroid belt,with individual masses in the range 0.017-0.33 Earth masses. In the simulations, these bodies undergo repeated close encounters which scatter one another into unstable resonances with the giant planets, leading to collision with the Sun or ejection from the Solar System. In response, the giant planets' orbits migrate radially and become more circular. This reduces the size of the main-belt resonances and the clearing rate, although clearing continues. If ~3 Earth masses of material was removed from the belt this way, Jupiter and Saturn would initially have had orbital eccentricities almost twice their current values. Such orbits would have made Jupiter and Saturn 10-100 times more effective at clearing material from the belt than they are on their current orbits. The time required to remove 90% of the initial mass from the belt depends sensitively on the giant planets' orbits, and weakly on the masses of the asteroidal planets. 18/25 of the simulations end with no planets left in the belt, and the clearing takes up to several hundred million years. Typically, the last one or two asteroidal planets are removed by interactions with planets in the terrestrial region.

c.)
Chambers, J. E., Lissauer, J.J., & Morbidelli, A., 2001, "Planet V and the Origin of the Lunar Late Heavy Bombardment" Bull. American Astron. Soc., 33, 1082

d.)
Chambers, J. E., & Cassen, P., 2002, "The effects of nebula surface density profile and giant-planet eccentricities on planetary accretion in the inner solar system", M & P Science, 37, pp. 1523-1540

Abstract
We describe results of 32 N-body planetary accretion simulations that investigate the dependence of terrestrial-planet formation on nebula surface density profile ? and evolution of the eccentricities of Jupiter and Saturn eJ,S. Two surface density profiles are examined: a decaying profile with ? ? 1/a, where a is orbital semi-major axis, and a peaked profile in which ? increases for a < 2 AU and decreases for a > 2 AU. The peaked profiles are generated by models of coagulation in an initially hot nebula. Models with initial eJ,S = 0.05 (the current value) and 0.1 are considered. Simulations using the decaying profile with eJ,S = 0.1 produce systems most like the observed planets in terms of mass-weighted mean a and the absence of a planet in the asteroid belt. Simulations with doubled ? produce planets roughly twice as massive as the nominal case. Most initial embryos are removed in each simulation via ejection from the Solar System or collision with the Sun. The asteroid belt is almost entirely cleared on a timescale of 10-100 Ma that depends sensitively on eJ,S. Most initial mass with a < 2 AU survives, with the degree of mass loss increasing with a. Mass loss from the terrestrial region occurs on a timescale that is long compared to the mass loss time for the asteroid belt. Substantial radial mixing of material occurs in all simulations, but is greater in simulations with initital eJ,S = 0.05. The degree of mixing is equivalent to a feeding zone of half width 1.5 and 0.9 AU for an Earth mass planet at 1 AU for the cases eJ,S = 0.05 and 0.1 respectively. In simulations with eJ,S = 0.05, roughly 1/3 and 5-10% of the mass contained in final terrestrial planets originated in the region a > 2.5 AU for the decaying and peaked profiles respectively. In the case eJ,S = 0.1, the median mass accreted from a > 2.5 AU is zero for both profiles.

2.)
Lubos Nelsusan on the other hand, basing his hypothesis on Titius Bode Law, contends that the Late Heavy Bombardment (who know (?) the source of water on Earth itself) and perhaps the formation of the moon may be due to the fact that the Earth WAS the "MISSING" Main Asteroid Belt planet. i.e. Some dramatic event/s must have occured early on to have resulted in the dramatic orbital migration of the Earth from the Main Belt to where it is today (i.e. 1 AU or 149,600,000 km). Titius Bode Law, Neslusan argues does NOT have a place for a planet in between the orbits of Venus and Mars and INSTEAD has room for one in between Mars and Jupiter.

Links to Dr. Lubos Neslusan&#39;s research:

http://astro.savba.sk/~ne/Publications/palermo2.ps
NOTE: Paper is in postscript format, for those on NON-Unix based platforms e.g. Windows, go download Ghostscript and then a Ghostscript Viewer for e.g. Windows

Neslusan, L., "Did the Earth migrate from the asteroid belt?", In Proc. Memorie della Societa, Astronomica Italiana, Spec. Vol.: Proc. Internat. Conf. held at Palermo, Italy, June 11-16, 2001, submitted

L. NESLUSAN
Queen Mary and Westfield College, University of London,
Mile End Road, London, E1 4NS, United Kingdom;

Abstract:
Assuming a possible migration of planets of solar system and/or their possible gravitational ejection in an interstellar space, we attempt to find a Titius-Bode-like law describing their mean-heliocentric-distance distribution. Some exceptions from a regular, power-function sequence &#036;<r_{n}> = r_{o} K^{n}&#036; could appear due to the migration and/or escape. For a set of combinations of such exceptions, we fit several power laws to the observed sequence of the planetary distances. The law, which is the best fit, predicts a planet in the region of main asteroid belt, but it does not predict any regular planet between the present orbits of Venus and Mars. To accept this law, we need to suppose an extraordinary way of creation of the Earth. It either originally accreted between the orbits of Mars and Jupiter and subsequently migrated into its present orbit (such a concept is supported by the giant-impact scenario of origin of the Earth-Moon system), or the proto-Jupiter scattered planetesimals away from the present asteroid-belt region enhancing their number density between the Venus and Mars, where no planet would have apperead, otherwise. Anyway, the asteroids in main belt seem to be remnant planetesimals related to our planet.

[rajasun]

You may also be interested in the following more layman and LESS technical write-up on Chambers et al.&#39;s hypothesis here:

http://www.space.com/scienceastronomy/sola...net_020318.html

Long-Destroyed Fifth Planet May Have Caused Lunar Cataclysm, Researchers Say
By Leonard David
Senior Space Writer
posted: 03:00 pm ET
18 March 2002


HOUSTON, TEXAS -- Our solar system may have had a fifth terrestrial planet, one that was swallowed up by the Sun. But before it was destroyed, the now missing-in-action world made a mess of things.

Space scientists John Chambers and Jack Lissauer of NASA&#39;s Ames Research Center hypothesize that along with Mercury, Venus, Earth, and Mars -- the terrestrial, rocky planets -- there was a fifth terrestrial world, likely just outside of Mars&#39;s orbit and before the inner asteroid belt.

Moreover, Planet V was a troublemaker.

The computer modeling findings of Chambers and Lissauer were presented during the 33rd Lunar and Planetary Science Conference, held here March 11-15, and sponsored by NASA and the Lunar and Planetary Institute.

It is commonly believed that during the formative years of our solar system, between 3.8 billion and 4 billion years ago, the Moon and Earth took a pounding from space debris. However, there is an on-going debate as to whether or not the bruising impacts tailed off 3.8 billion year ago or if there was a sudden increase - a "spike" -- in the impact rate around 3.9 billion years ago, with quiet periods before and afterwards?


This epoch of time is tagged as the "lunar cataclysm" - also a wakeup call on the cosmological clock when the first evidence of life is believed to have appeared on Earth.

The great cover-up

Having a swarm of objects clobbering the Moon in a narrow point of time would have resurfaced most of our celestial next door neighbor, covering up its early history. Being that the Moon is so small, Earth would have been on the receiving end of any destructive deluge too.

Moon-walking astronauts brought back a cache of lunar material. Later analysis showed that virtually all impact rocks in the "Apollo collection" sported nearly the same age, 3.9 billion years, and none were older. But some scientists claim that these samples were "biased", as they came from a small area of the Moon, and are the result of a localized pummeling, not some lunar big bang.

There is a problem in having a "spike" in the lunar cratering rate.

That scenario is tough to devise. Things should have been settling down, according to solar system creation experts. Having chunks of stuff come zipping along some hundreds of millions of years later out of nowhere and create a lunar late heavy bombardment is a puzzler.

If real, what were these bodies, and where were they before they scuffed up the Moon big time? The answer, according to Chambers and Lissauer, might be tied to the Planet V hypothesis.

"The extra planet formed on a low-eccentricity orbit that was long-lived, but unstable," Chambers reported. About 3.9 billion years ago, Planet V was perturbed by gravitational interactions with the other inner planets. It was tossed onto a highly eccentric orbit that
crossed the inner asteroid belt, a reservoir of material much larger than it is today.

Planet V&#39;s close encounters with the inner belt of asteroids stirred up a large fraction of those bodies, scattering them about. The perturbed asteroids evolved into Mars crossing orbits, and temporarily enhanced the population of bodies on Earth-crossing orbits, and also increased the lunar impact rate.

After doing its destabilizing deeds, Planet V was lost too, most likely spinning into the Sun, the NASA team reported.

The temporary existence of more than 4 planet-sized bodies in the inner Solar System is consistent with the currently favored model for the formation of the Moon. Work by Chambers and Lissauer also supports the view that our Moon is a leftover of a massive collision between Earth and a Mars-sized body 50 million to 100 million years after the formation of the Solar System.

Striking view

Wendell Mendell, a planetary scientist here at NASA&#39;s Johnson Space Center, said the new theory is intriguing.

"This idea and others within the last few years show that the Solar System is filled with all sorts of gravitational resonances...that a lot of potential orbits in the Solar System are chaotic and unstable," Mendell told SPACE.com. "My sense is that this is a new idea. It&#39;s another thing to throw into the pot that&#39;s not totally crazy."

The work suggests there&#39;s a match up in timing, Mendell said, with asteroids striking the Moon and causing the effects that are seen in the dating of Apollo lunar rocks.

"By thinking that the Solar System was really quite different in a major way with an extra inner planet, we might be able to develop some sort of self-consistent scenario that explains a lot of things. But all this is at the very early stages now," Mendell said.

"We&#39;re moving into a really new regime," Mendell added, "where the Solar System is not a static dynamic place from day one to now. It really might have had some nuances and synchronicities associated with it that we have not really tried to exploit before."

It takes a drill hole Setting the early Solar System and lunar history record straight means going back to the Moon.

"The Moon is still the keystone to our understanding of the Solar System," NASA&#39;s Mendell said.

That too is the view of Apollo 17 astronaut, Harrison "Jack" Schmitt. Getting back to the Moon to sort out the real story is a must, he said.

"You&#39;re going to have to be very, very specific on what sites you go to collect new samples," Schmitt told SPACE.com. "It may be very difficult to get an answer without using missions to fairly large impact craters that penetrate through the ejecta. Those impacts are sort of a drill hole into the lunar crust," he said.

Dating service

Places on the Moon where older, large basins have deposited ejecta are ideal research zones, Schmitt said. Digging into such sites could yield impact glass formed by basins perhaps dating older than 3.9 billion years old, he said.

Just taking spot samples -- say from the Moon&#39;s South Pole Aitken basin -- could be risky, in terms of uncovering the Moon&#39;s rocky history, Schmitt said. Such a huge area would take multiple robotic or human exploration missions, each with significant roving abilities.

Also known as the "Big Backside Basin," Aitken is the largest impact crater on the Moon, and one of the biggest in the Solar System.

For the near term, sets of low-cost, mini-robotic landers carrying specialized gear would be ideal in opening up the Moon to further exploration, Schmitt said.

"Numbers of targeted missions could get a lot of great information on some of these fundamental questions that we still haven&#39;t been able to answer," Schmitt said.

Getting back to the Moon with a settlement for resource exploitation is another step forward. From such a site, human explorers can survey various lunar locales - even the Moon&#39;s side that we Earthlings never see, Schmitt said. "Then we can do the kind of thing that Apollo did for the near side of the Moon," he said.

Hope this helps&#33;

B)

[damienpaul]

Yes that does help, I have a sort of related question...is it possible that a planet does go in perpendicular orbit through that field or had in the past...?

[rajasun]

Originally posted by damienpaul@Dec 20 2003, 02:43 PM
Yes that does help, I have a sort of related question...is it possible that a planet does go in perpendicular orbit through that field or had in the past...?

UNLIKELY VERY UNLIKELY for a planet or planetoid to survive long WITHOUT being removed via the operation of the Kozai Mechanism damienpaul.

For an understanding on what the Kozai Mechanism is...do a search at EITHER of these places:
1.) http://adsabs.harvard.edu/abstract_service.html
2.) where else? BUT google <_<

Sorry for the LATE reply though was busy with the arithmatics and theory at another thread >>>
http://www.universetoday.com/forum/index.p...view=getnewpost

i.e. thread on a Hypothetical BD Companion to the Sun

B)

[damienpaul]

Thank you for that rajasun, it will help me win a debate also&#33; dang smartypants students of mine&#33;&#33;&#33;&#33;&#33;&#33;&#33; :P

[rajasun]

NO probs matey. Hmmm NT Australia, isn&#39;t it hmmm Sunday, Dec 21, 0015 Hours already matey? I&#39;m from a place very near to where you are hehehe... h34r:

[damienpaul]

well it is 01:45 here, so you must be west of me&#33;&#33;&#33;&#33;&#33; peers westward h34r:

[rajasun]

Hmmm do they have Daylight Saving down in Alice Springs too? hmmm... h34r:

Well time to go for me...gotto go check on the EPL results on BBC World...G&#39;Day and see you around, matey&#33; B)

[damienpaul]

no daylight savings....Central Standard time is 1.5 hours ahead of western standard time for the Australian part of this oversized asteroid&#33;