  One of the main evolutionary stages of planet formation is the dynamical
evolution of planetesimal disks. These disks are thought to evolve through
gravitational encounters and physical collisions between single planetesimals.
In recent years, many binary planetesimals have been observed in the Solar
system, indicating that the binarity of planetesimals is high. However, current
studies of planetesimal disks formation and evolution do not account for the
role of binaries. Here we point out that gravitational encounters of binary
planetesimals can have an important role in the evolution of planetesimal
disks. Binary planetesimals catalyze close encounters between planetesimals,
and can strongly enhance their collision rate. Binaries may also serve as
additional heating source of the planetesimal disk, through the exchange of the
binaries gravitational potential energy into the kinetic energy of
planetesimals in the disk.
