Terrestrial planet region, Solar System

Chondrules comprise the major portion of most chondrites, the most abundant type of meteorites. If the achondrites and terrestrial planets formed from chondrite-like precursors, then much, perhaps most of the solid matter in the inner solar system once existed as chondrules. Even if chondrules were restricted to the chondrites, the process that formed them was important in that region. The origin of chondrules is an important unsolved problem in cosmochemistry. Chondrules formed in the Sun s accretion disk through some sort of transient flash-heating event(s). Some CAIs apparently also were melted in the disk. What was the process (or processes) that melted the chondrules and CAIs Whatever it was, it dominated the disk for at least a few million years. 

Asteroids, comets and smaller particles are also grouped into SSSBs, small solar system bodies. All categories of objects described above appear at specific locations in the solar system. The inner solar system contains the terrestrial planets and the Main Belt of asteroids. In the middle region there are the giant planets with their satellites and the centaurs. The outer solar system comprises the Trans-Neptunian objects including the Kuiper Belt, the Oort cloud, and the vast region in between. 

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