Migration of dust particles to the terrestrial planets
  The orbital evolution of asteroidal, trans-Neptunian, and cometary dust particles under the gravitational influence of planets, the Poynting-Robertson drag, radiation pressure, and solar wind drag was integrated. Results of our runs were compared with the spacecraft observations of the number density of dust particles and with the WHAM observations of velocities of zodiacal particles. This comparison shows that the fraction of cometary dust particles of the overall dust population inside Saturn's orbit is significant and can be dominant. The probability of a collision of an asteroidal or cometary dust particle with the Earth during its dynamical lifetime is maximum at diameter about 100 micron. 
S. I. Ipatov and J. C. Mather