  Most of the objects in the trans-Neptunian belt (TNb) and related populations
move in prograde orbits with low eccentricity and inclination. However, the
list of icy minor bodies moving in orbits with an inclination above 40 deg. has
increased in recent years. The origin of these bodies, and in particular of
those objects in retrograde orbits, is not well determined, and different
scenarios are considered. 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' matter typical of some Centaurs. Despite small
differences, 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 for
their reddish- to neutral-color. To investigate if the surface properties and
dynamical evolution of these bodies are related, we integrate their orbits for
10^(8) years to the past. We find a remarkable difference in their dynamical
evolutions: 2005 VD' s evolution is dominated by a Kozai resonance with planet
Jupiter while that of 2008 YB3 is dominated by close encounters with planets
Jupiter and Saturn. Our models suggest that the immediate site of provenance of
2005 VD is the in the Oort cloud, whereas for 2008 YB3 it is in the
trans-Neptunian region. Additionally, the study of their residence time shows
that 2005 VD has spent a larger lapse of time moving in orbits in the region of
the giant planets than 2008 YB3. Together with the small differences in color
between these two objects, with 2005 VD being more neutral than 2008 YB3, this
fact suggests that the surface of 2005 VD has suffered a higher degree of
processing, probably related to cometary activity episodes.
