Rubble Pile Asteroid

Cutaway view inside a rubble pile asteroid. Image Credit: Modified from Porosity and Internal Composition of Asteroids by Consolmagno

A type of asteroid held together by friction and mutual gravitation consisting of loose jumbled rock fragments from potentially different parent body sources, and often containing large voids. Rubble pile asteroids can can contain material accumulated from many previous collisions with disparate geologic histories. During these collissions and other impacts, the surface of the asteroid will become regolith. For example, when the asteroid 2008 TC3 fell to Earth as the meteorite Almahita Sitta, many different types of meteorites were found including but not limited to various ureilite types, EH chondrites and even a bencubbinite. Many of the smaller asteroids are thought to be rubble piles based on their density being (much) lower than ice or various meteorite types. Due to their loose composition and self-gravity, rubble pile asteroids cannot spin faster than about one rotation every 2.2 hours in order for them to maintain their structural integrity. Said another way, any faster and they would fly apart1.