A "rubble pile" is a type of small Solar System body, such as an asteroid or comet, that is composed of a loose agglomeration of smaller rocky or icy fragments held together by gravity. These bodies are thought to have formed from the accumulation of debris left over from the early Solar System, rather than being a single solid object. Rubble piles are of interest to researchers because they can provide insights into the processes of planetary formation and the dynamics of small bodies in the Solar System. Studies of rubble piles involve observations of their physical properties, such as their shape, density, and composition, as well as modeling their formation and evolution. Additionally, rubble piles may pose a threat to Earth if they were to collide with our planet, making understanding their characteristics and behavior important for planetary defense efforts.