Collisional activation of asteroids in cometary orbits

C. G. DÍAZ Y R. GIL-HUTTON

ASTRONOMY AND ASTROPHYSICS

Año: 2008 vol. 487 p. 363 - 367

0004-6361

aims: In this work we study the time an asteroid in cometary orbit must wait to receive a collision producing a crater depth enough to expose subsurface volatiles, aiming to analyze the possibility of collisional reactivation of these objects in the case that they are dormant comets.methods: We made a numerical integration of the asteroids in cometary orbits and a population of projectiles to found the mean intrinsic collision probabilities and mean impact velocities of the targets. The projectile population were obtained as a sample with the same distribution of orbital elements observed for main belt asteroids, and we also take into account that its size distribution changes for different size ranges. Only 207 asteroids in cometary orbits which are not members of other asteroid groups, with Tisserand parameter 2< T_J < 2.9, and perihelion distance q>1.3 AU were considered.results: A large fraction of the objects in the ACOs sample receive at least 1 collision energetic enough to break the comet crust and allow a dormant comet to reach an active state in a period shorter than a JFC dynamical lifetime. A large fraction of the objects in the ACOs sample with r_t> 8-9 km receive several collisions and could be active during more than 3x10^4 yr. We found an excess in the number of dormant comet candidates from the expected values which is indicative of the presence in the ACOs population of objects which are not comets in a dormant state. These objects could be asteroids with T_J<3 obtaining their present orbits by some dynamical mechanism that perturbs the original asteroidal orbit changing its Tisserand invariant.