  We discuss the probability distribution of relative speed $\Delta V$ of
inertial particles suspended in a highly turbulent gas when the Stokes numbers,
a dimensionless measure of their inertia, is large. We identify a mechanism
giving rise to the distribution $P(\Delta V) \sim \exp(-C |\Delta V|^{4/3})$
(for some constant $C$). Our conclusions are supported by numerical simulations
and the analytical solution of a model equation of motion. The results
determine the rate of collisions between suspended particles. They are relevant
to the hypothesised mechanism for formation of planets by aggregation of dust
particles in circumstellar nebula.
