Collisional evolution is a research area within planetary science that focuses on how celestial bodies, such as planets, moons, asteroids, and comets, evolve over time due to collisions with other objects in space. This research involves studying the frequency, impacts, and effects of collisions on the structure, composition, and dynamics of planetary bodies. By analyzing the outcomes of these collisions, scientists can gain a better understanding of the formation and evolution of our solar system and other planetary systems throughout the universe.