The study investigates the physical properties of asteroid Dimorphos, the target of NASA's Double Asteroid Redirection Test (DART) mission, which successfully impacted it on September 26, 2022. Numerical simulations are used to match the observed momentum deflection efficiency, ejecta cone geometry, and ejected mass. The simulations indicate that Dimorphos is a weak, low-density body with a bulk density of less than 2,400 kg m\(^{-3}\) and a low volume fraction of boulders (≤40 vol%). These findings suggest that Dimorphos is a rubble pile, possibly formed through rotational mass shedding and reaccumulation from Didymos. The DART impact caused global deformation and resurfacing of Dimorphos, and the upcoming ESA Hera mission may find a reshaped asteroid rather than a well-defined crater. The study also explores the ejecta cone opening angle and morphology, finding that the observed cone angle is consistent with low cohesion on the asteroid's surface. The results provide valuable insights into the formation and characteristics of binary asteroids and have implications for planetary defense strategies.The study investigates the physical properties of asteroid Dimorphos, the target of NASA's Double Asteroid Redirection Test (DART) mission, which successfully impacted it on September 26, 2022. Numerical simulations are used to match the observed momentum deflection efficiency, ejecta cone geometry, and ejected mass. The simulations indicate that Dimorphos is a weak, low-density body with a bulk density of less than 2,400 kg m\(^{-3}\) and a low volume fraction of boulders (≤40 vol%). These findings suggest that Dimorphos is a rubble pile, possibly formed through rotational mass shedding and reaccumulation from Didymos. The DART impact caused global deformation and resurfacing of Dimorphos, and the upcoming ESA Hera mission may find a reshaped asteroid rather than a well-defined crater. The study also explores the ejecta cone opening angle and morphology, finding that the observed cone angle is consistent with low cohesion on the asteroid's surface. The results provide valuable insights into the formation and characteristics of binary asteroids and have implications for planetary defense strategies.