Collisional and Dynamical Evolution of Plutinos

GONZALO C. DE ELÍA; ADRIÁN BRUNINI; ROMINA P. DI SISTO

Río de Janeiro, Brasil

Simposio; Simposio 263 de la IAU: "Icy Bodies of the Solar Sytem"; 2009

In this work, we analyze the collisional and dynamical evolution of thepopulation of Plutinos, which reside in the 3:2 mean motion resonance withNeptune, at ~ 39.5 AU from the Sun. To do this, we construct a statisticalcode, which evolves in time the number of bodies residing in a given set ofsize bins. Here, we test different collisional parameters and include adynamical treatment that takes into account the stability and instabilityzones of the 3:2 Neptune resonance. This procedure allows us to estimate thesize distribution of Plutinos, to study their mean collisional lifetimes, toanalyze the formation of families, to obtain ejection rates of fragments fromthe resonance and to discuss their possible contribution to the eclipticcomet population. Our simulations are developed assuming the existence of onePluto-sized object in the 3:2 Neptune resonance. The Plutino populationlarger than a few kilometers in diameter is not significantly altered bycatastrophic collisions over the age of the Solar System. Thus, we infer thatthe break suggested by previous works at a diameter D near 40-80 km in thePlutino cumulative size distribution should be primordial and not a result ofthe collisional evolution. The existence of such a break is still a matter ofdebate. On the other hand, our analysis indicates that 8 large families areformed in the 3:2 Neptune resonance over the Solar System history. ConcerningPlutino removal, we find that one object with a diameter D > 1 km is ejectedfrom the 3:2 resonance with Neptune every ~ 400-1900 yr. Then, we study thesensitivity of our results to the number of Pluto-sized objects in the 3:2Neptune resonance. Our simulations suggest that the larger the number ofPluto-sized bodies, the higher the ejection rate of fragments from thatresonant region and the number of families formed over 4.5 Gyr. Thus, if amaximum of 5 Pluto-sized objects are assumed to be in the 3:2 Neptuneresonance, one body with a diameter D > 1 km is ejected every tens of yearswhile ~ 170 large families are formed over the Solar System history. Fromthese estimates, we conclude that it is necessary to specify the number ofPluto-sized objects present in the 3:2 Neptune resonance to determine if thisregion can be considered an important source of ecliptic comets. Finally, wefind that the current orbital distribution of the Plutinos does not offer astrong constraint on the dynamical origin of this population.