Surface Composition and Dynamical Evolution of Two Retrograde Centaurs

N. PINILLA-ALONSO, A. ALVAREZ-CANDAL, M. MELITA, V. LORENZI, J. LICANDRO, J. CARVANO, D. LAZZARO, G. CARRARO, V. AL-LAGOA AND E. COSTA.

ICARUS

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2012 p. 1 - 1

0019-1035

Most of the objects in the trans-Neptunian belt and related populations move in prograde orbits with low eccentricity and inclination.However, the list of minor icy bodies moving in orbits with an inclination above 40 has increased in the last years. The origin of thesebodies, and in particular of those objects in retrograde orbits, is not well determined and dierent scenarios are considered, dependingon their inclination and perihelion. In this paper we present new observational and dynamical data of two objects in retrograde orbits,2008 YB3 and 2005 VD.We find that the surface of these extreme objects is depleted of ices and does not contain the ?ultra-red? mattertypical of some Centaurs. Despite small dierences, these objects share common colors and spectral characteristics with the trojans,comet nuclei and the group of grey centaurs. All of these populations are supposed to be covered by a mantle of dust responsible fortheir reddish to neutral color. To investigate if the surface properties and dynamical evolution of these bodies are related we integratetheir orbits for 108 years to the past.We find a remarkable dierence in their dynamical evolutions: 2005 VD?s evolution is dominatedby a Kozai resonance with planet Jupiter while that of 2008 YB3 is dominated by close encounters with planets Jupiter and Saturn.Additionally, the study of their residence time shows that 2005 VD has spent a larger lapse of time moving in orbits in the region ofthe Giant Planets than 2008 YB3. This fact, together with the small dierences in color between these two objects, being 2005 VDmore neutral than 2008 YB3, suggests that the surface of 2005 VD has suered a higher degree of processing by irradiation and/orcometary activity.