A 2007 US-Czech study decided that 298 Baptistina may be the biggest remnant of a 170 km ( 110 mile ) asteroid that was destroyed about 160 million years ago in an impact with a smaller body , making the Baptistina family of asteroids and that the Baptistina event may have created the eventual impact asteroid believed by many to have caused the Cretaceous â `` Tertiary extinction event about 65 million years ago . . Further , the study argues that the family is the remnant of a 170 km ( 110 mile ) parent asteroid that was destroyed in a collision with a smaller body some 160 million years ago , with Baptistina itself being the largest remnant . Moreover , it suggests that a fragment from this event eventually became the K\/T impactor believed to have caused the Cretaceousâ `` Tertiary extinction event that brought about the extinction of the dinosaurs 65 million years ago .