"Theories regarding the formation of the asteroid belt from the destruction of a hypothetical fifth planet are today collectively referred to as the "disruption theory". This theory states that there was once a major planetary member of the solar system circulating in the present gap between Mars and Jupiter, which was variously destroyed when:The planet is most often called Phaeton. But sometimes Astra.
it veered too close to Jupiter and was torn apart by the gas giant's powerful gravity.
it was struck by another large celestial body.
it was destroyed by a hypothetical brown dwarf, the companion star to the Sun known as Nemesis.
it was shattered by some internal catastrophe.
Space There is a theory that the asteroid belt was the product of a notional "fifth" planet which existed between the orbits of Mars and Jupter until a cataclysm led to its destruction.