Hilda asteroids among Jupiter Family Comets

ROMINA P. DI SISTO; ADRIÁN BRUNINI; LORENA DIRANI; ROSA B. ORELLANA

ICARUS

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam, The Netherlands.; Año: 2005 vol. 174 p. 81 - 89

0019-1035

Hilda asteroids and comets are similar from the compositional point of view. The D -taxonomic class prevailing among Hildas have all the characteristics found in the comets espectrum. Jupiter Family Comets (JFC) enter the planets zone  from the Trans Neptunian region, having encounters with the outer planets, mainly with Jupiter.  As a result they are reducing their perihelion distances  until they show activity becoming observable. The gravitational control of Jupiter on JFC, makes them dynamicaly unstable. Hilda asteroids residing in the 3:2 mean motion resonance with Jupiter are, on the contrary,  a very stable population. But once escaped from the resonance, they are dynamically controlled by Jupiter and in this sense they resemble the JFC behaviour. We performed a numerical simulation  to analyze the dynamical evolution  Hildas follow after escape from the resonance, and their contribution to the JFC population. We obtain that the $78.2 %$ of particles left the resonance with the 8% of them impacting Jupiter. From the escaped bodies, the (98.7 %) live at least 1000 years like  JFC with a mean life of 1.4 x 10^6  years. In particular escaped Hildas stay mainly in the region of perihelion distances grater than 2.5 A.U., contributing with the 14 % to the JFC in that zone. On the contrary, the number of escaped Hildas in the inner zone ( q < 2.5 A.U.) is negligible.  So, there are almost non Hildas among the NEO population. We analyzed also the possibility that the Shoemaker - Levy 9 was a Hilda asteroid. If it were, it would be possible to fix their pre-capture orbital elements.