  The formation of the first planetesimals and the final growth of planetary
cores relies on the abundance of small pebbles. The efficiencies of both the
streaming instability (SI) process, suggested to catalyze the early growth of
planetesimals, and the pebble-accretion process, suggested to accelerate the
growth of planetary cores, depend on the sizes of solids residing in the disk.
In particular, these processes were found to be sensitive to size distribution
of solids, and efficient planetesimal formation and growth through these
channels require a limited pebble size distribution. Here we show that aeolian
erosion, a process that efficiently grinds down boulders into a mono-sized
distribution of pebbles, provides a natural upper limit for the maximal pebble
sizes (in terms of their Stokes number). We find the dependence of this upper
limit on the radial separation, disk age, turbulence strength, and the
grain-size composition of the boulders in the disk. SI is favorable in areas
with a Stokes number less than 0.1, which is found in the inner
sub-astronomical-unit regions of the disk. This upper limit shapes the size
distribution of small pebbles and thereby catalyzes the early onset of
planetesimal formation due to SI, and the later core accretion growth through
pebble accretion.
