  The Classical Kuiper Belt is populated by a group of objects with low
inclination orbits, reddish colors and usually belonging to a binary system.
This so called Cold Classical Kuiper Belt is considered to have been formed in
situ from primordial ice pebbles that coagulated into planetesimals hundreds of
kilometers in diameter. According to this scenario, the accretion of pebbles
into large planetesimals would have occurred through the streaming instability
mechanism that would be effective in the primordial Solar System disk of gas
and solids. Nevertheless other objects with the same color characteristics as
those found in the Cold Classical Kuiper Belt can be encountered also past the
2:1 mean motion resonance with Neptune as scattered or detached objects. Here I
propose a mechanism that can account for both the cold Classical Kuiper Belt
objects and other reddish objects outside the Classical Kuiper Belt. According
to the proposed scenario, reddish objects were primordially in the outer
portion of the planetesimal disk which was however truncated somewhere below 42
au. In this manner the cold Classical Kuiper Belt and its scattered / detached
counterpart were respectively transported outwards by a short range or slightly
scattered to their present locations. Resonant objects were also formed by the
same process. This mechanism is aimed at explaining the distribution of all
objects that share the same color characteristics as coming from a common
origin in the outer borders of the primordial planetesimal disk. According to
the scenario here proposed the Cold Classical Kuiper Belt would have been
formed around 4 au inside its present location with a total mass 20 to 100
times as large as its present value.
