But small bodies such as comets have very little gravity, so gravitational contraction does not generate enough heat within them to cause such changes. Thus they remain in the same state as they were in when the solar system formed. The scientific purpose of investigating them is to understand the origins of the solar system.
彗星等小星體無法因自身萬有引力壓縮、產生足夠熱量發生改變，因此保存了早期太陽系形成時的狀態，探測彗星物質的科學目的，正是想瞭解太陽系的起源與演化。