According to one theory, earth's moon accreted to form its current structure following a giant impact between earth and another celestial body complete the paragraph to describe the process of accretion following the impact, a section of earth broke off. as a result, large pieces of debris started to revolve around earth. the debris was held close to earth by earth's the debris frequently collided to form a planetesimal. as the planetesimal grew in size, its gravity increased. this gravitational force pulled in even more which led to the accretion of the moon.