kinda long, but neat...
http://www.ascensionearth2012.org/2014/04/did-planet-in-our-solar-system-explode.html

Following is a synopsis of evidence presented by Tom Van Flandern. in his book Dark Matter, Missing Planets and New Comets (Paradoxes Resolved, Origins Illuminated) in the chapter titled "A Synthesis of Recent Planetary Breakup Evidence" (pages 215 - 236).

Evidence Related to Asteroids
Evidence Related to Comets
Evidence Related to Planets and their Moons
Other Miscellaneous Evidence

Evidence Related to Asteroids
The asteroids inhabiting the belt between Mars and Jupiter have tilts and ellipticity that don't conform with the theory that they condensed in the same manner that the planets did.
The mean relative velocities between asteroids (about 5 km/sec) are more indicative of a breakup and not of formation from a solar nebula.
The asteroids should be highly fragmented due to the predicted mean time between collisions (about 5% the age of the solar system). Because they are not suggests that their formation is recent.
The asteroids show the same characteristic distribution as fragments from exploded satellites orbiting the Earth.
The Kirkwood gaps in the asteroid belt appear to be a natural result of an explosion but cannot be easily explained in the conventional asteroid formation theory.
Asteroid satellites appear to be common. Satellites would be a natural byproduct of an explosion origin, but highly unlikely in the conventional theory.
Tidal forces and collisions should have eliminated most asteroid satellites long ago (assuming they formed when the planets did). This also implies that the asteroids are much younger then previously believed.
There still are about 1000 asteroids larger then 1 km in Earth-crossing orbits. These should have been virtually eliminated, mostly by Earth collisions, in about 30,000,000 years. This again suggests that asteroids are very young.
Evidence Related to Comets
Lagrange pointed out in 1814 that the elongated orbits of comets would be a natural byproduct of an explosion in the solar system, but are not consistent with formation through condensation from a nebula.
Comets are conventionally thought to come from the "Oort cloud," a theoretical cloud containing more than a trillion comets orbiting the sun about 1000 times farther out then Pluto. The exploded planet theory offers a viable and simple alternative to this hypothesis.
Many new comets coming from the "Oort cloud" develop tails at 2.8 au from the Sun. The exploded planet theory places comet origins at 2.8 au (the location of the exploded planet). When these comets pass 2.8 au for the first time, orbiting material is able to escape due to the shrinking gravitational sphere of influence of the comet. This escaping matter forms the tail of the comet. (Note: Dr. Tom Van Flandern hypothesizes that comets are simply asteroids that were flung into large elliptical orbits from the explosion and thus have the same origin as asteroids. This contradicts the common belief that comets are "dirty snowballs" of volatiles.)
The ratio N2/NH3 was observed at 1/10 for Haley's Comet, contrary to the 100-200 ratio for conventional comet models. This suggests a comet origin much closer to the sun then the outer solar system or farther out, as the conventional models suggest.
84% of comets arrive from one hemisphere of the sky and 16% from the other (after correction for selection events). This is required by the exploded planet theory. Comets originating from the "Oort cloud" should have a more uniform ratio.
The optical reflectivity of asteroids and comets is very low, as expected from the charred residue of an explosion. The dirty snowball model of comets predicts ice, which is lacking in the reflection spectra of comets.
New comets loose an order of magnitude in brightness on their first approach to the Sun, but old comets show no further decrease in brightness. This holds if the comets are asteroid type entities. On their first approach to the Sun they would loose satellites as their gravitational sphere of influence shrank, but on subsequent passes all the satellites that would have escaped have already done so.
Evidence Related to Planets and their Moons
Mercury's slow rotation would cause one hemisphere of the planet to be more heavily cratered during the initial blast wave. This cratering characteristic has been observed.
The abundance of deuterium on Venus relative to hydrogen indicates abundant water in the past, more than can be accounted for by comet impacts alone. (Note: The missing planet is theorized to have had an abundance of water which would have been ejected during the explosion.)
Tektites, a meteorite found on earth, may be the remains of the initial blast wave. These glassy meteorites were melted prior to entering the Earth's atmosphere (entering the atmosphere also re-melted the objects). The planetary explosion provides a natural source for these meteorites.
The Earth's climate changed from warm, equatorial-like conditions (uninterrupted for 50,000,000 years) to a succession of ice ages over the past 3,000,000 years or so. A massive influx of water vapor from the explosion event may have been responsible for this.
Regions of the Earth show evidence for a massive flood several million years ago. The Spokane Flood evidence indicates a short-lived event involving not less than 2000 cubic kilometers of water discharged per day. This could have been caused by a major impact event in the Pacific Ocean, or a direct result of a massive influx of water from the breakup event.
The calculated cratering rate on the Earth and the Moon from the present populations of Earth-crossing comets and asteroids exceeds the total observed cratering by a factor of eight. This discrepancy would be easily explained if the impactor population has been this high for only the last few million years.
The breakup event could help explain the origin of magnetism in lunar rocks as well as radioactivity in lunar soil, neither of which can be native to the Moon.
Mars shows direct evidence for a recent influx of cratering in the form of a number of small, fresh craters. It is conventionally thought that the larger, older craters were obliterated suddenly by some unknown past event.
Martian winds and sand should erode craters at the rate of 200 meters per million years. Craters older than 100 million years should be long gone, but Mars is covered with craters.
Mars shows evidence that there was enough water for a brief period of time to produce flowing rivers and channels. Sinuous rilles on the Moon and Mars are almost certainly water-carved features and relatively recent as well (as indicated by the lack of overlay craters). The theory that these rilles are the result of lava flows is inconsistent (lava is not known to carve sinuous features). Comets and asteroids appear to be about 20% water by bulk, suggesting that the breakup event could have been the source of a sudden, short-lived, massive influx of water. It is known that water flow on an airless body is possible, since ice forms immediately over the surface, preventing evaporation of the flowing water beneath.
Phobos will tidally decay into the Martian atmosphere in about 30-40 million years, only 1% the age of the solar system. This is less coincidental if Phobos originated 3,200,000 years ago as a captured asteroid from the explosion event.
A gap in the spacing between the planets Mars and Jupiter is large enough to accommodate a missing planet. Jupiter's mass is insufficient to have interfered with the formation of a normal planet at this location.
Jupiter will have swept up almost all the mass from the exploded planet that did not escape the solar system. Jupiter's excess heat flux over what it receives from the Sun may be an indication of relatively recent mass accretion by the planet
The "Great Red Spot" on Jupiter (as well as other similar spots on the gas giants) may be the site of an unusually large impact, perhaps from one of the largest surviving fragments from the explosion event. The debris may now be held together by gravitation and cohesion, and remain floating in the planet's atmosphere.
All atmosphere-less bodies in the outer solar system are coated with an extremely dark material. This may be the carbonaceous residue from the blast Those which rotate more slowly than one month (Iapetus and possibly Nereid) are coated on only one side. Pluto, which can rotate pole-on at times, is coated on holy one hemisphere. Triton, whose orbital tilt hides one polar region from view for years at a time, is coated everywhere except the southern polar regions, which are icy bright.
Spectrally, the dark material on outer solar system satellites is the same as Type C and Type D asteroids, both of which are associated with carbonaceous chondrite meteorites.
Other Miscellaneous Evidence
AT the present time our solar system is embedded in a uniform, X-ray absorption-free emitting region of variable extent. Evidence indicates that the X-rays originate within a few hundred parsecs and may be associated with gamma-ray bursts. The observed background soft X-ray and extreme ultraviolet spectra seem to suggest that an energetic explosion of possibly supernova proportions occurred within the last 4,000,000 years, affecting the interstellar medium surrounding the Sun.
Radio scintillation maps suggest that the solar neighborhood is encapsulated in an envelope of plasma turbulence, conventionally thought to be the relic of a supernova explosion of a nearby massive star.
Unless the exploded planet was a lot less massive than the evidence suggests, chemical or collisional processes do not generate enough energy to blow it apart. Nuclear processes are indicated by meteoritic evidence. It has been objected that planets are not hot enough in their cores for nuclear reactions, yet natural surface fission reactors have been known to operate even on the Earth's surface in the geologic past. But the most natural way to produce the isotopic anomalies observed in meteorites, and supply abundant energy, is by a matter-antimatter explosion. This speculative possibility might result from magnetic separation and storage of the antimatter in a planet over billions of years before the explosion; or from some sort of chain-reaction high-energy antimatter generation process; or from the intervention of intelligent beings (which shouldn't be dismissed out of hand).
The primary source of gamma-ray bursts must be within 500 parsecs, because of their uniformity over the sky, and the lack of indicators of cosmological distances. Fainter bursts do concentrate toward the galactic plane, but must still lie within a few kiloparsecs of the Sun, and cannot be spread uniformly throughout space or within our galaxy. There is a great variety of observed bursts with unknown sources, which fail to match up with known astronomical objects at any other wavelengths. There are abundant bright bursts, but a deficit of faint bursts. Some spikes have durations as short as 0.2 milliseconds, requiring either relativistic beaming or small source bodies, probably only kilometers across. This picture would be neatly explained by an exploding shock wave from the planetary explosion event, producing such bursts whenever it ran into matter in any form. Specifically, the high energy of gamma-ray bursts would be a natural consequence of antimatter from the explosion encountering interstellar matter.
Evidence for the local bubble in the interstellar medium exists in observations at all wavelengths from gamma-ray through radio. There also appears to be a trough in the nearby interstellar dust which is roughly Sun-centered. This evidence supports the planetary explosion hypothesis.

One theory i know of the origin of the Asteroid Belt comes from the research of the late Zechariah Sitchin. He elaborately explained it in his books, The 12th Planet and Genesis Revisited.

it never really made sense to me that the asteroid belt was formed at the birth of the solar system... i'm not real sure what genesis has to do with science tho...

Your right, the asteroid belt wasnt present yet at the birth of the solar system. Based on the info i've read from those books, it was a planet first. Half of it turn to pieces that became the asteroid belt and the other half became Earth.I'm not answering to argue..i dont like arguments, these infos i enjoyed reading bcoz they are not taught in school. I just love Science.

me too!

It is estimated that at least a hundred planets have formed since the formation of the solar system. They smacked into each other over and over to leave what exists now. Some science sources say that the asteroids were left overs from the original solar system formation but common sense and simple physics says that the accretion of the particles will not form the solid rocks that make up most asteroids. However, accretion will form the type of objects that make comets.

As the large planets and the Sun ate the wandering debris in our system, eventually what was left is what you see now. The asteroid belt was probably a planet or parts of more than one planet that didn't survive the maelstrom of flying rocks in our system.

When a planet is formed, the heavy metals mostly sink to the center of the molten mass. It is estimated that a single asteroid formed from the center of an exploded planet, could supply all of Earth's need for heavy metals.

Very interesting..