What astronomical feature separates the inner rocky worlds from the outer icy worlds by defining where volatiles freeze?

Answer

The frost line (or snow line)

The temperature gradient created distinct chemical zones separated by the frost line, or snow line, beyond which volatile compounds like water, methane, and ammonia could freeze into solid ices.

What astronomical feature separates the inner rocky worlds from the outer icy worlds by defining where volatiles freeze?
solar systemformationhypothesiscreation