Astronomical Evidence for the Rapid Growth of Millimeter Sized Particles
  in Protoplanetary Disks
  I summarize recent surveys of protoplanetary disks at millimeter wavelengths
and show that the distribution of luminosity, equivalent to the mass in small
dust grains, declines rapidly. This contrasts with statistics on the lifetime
of disks from infrared observations and the high occurrence of planets from
radial velocity and transit surveys. I suggest that these disparate results can
be reconciled if most of the dust in a disk is locked up in millimeter and
larger sized particles within about 2 Myr. This statistical result on disk
evolution agrees with detailed modeling of a small number of individual disks
and with cosmochemical measurements of rapid planetesimal formation.
