  Probabilities of collisions of migrating small bodies and dust particles
produced by these bodies with planets were studied. Various Jupiter-family
comets, Halley-type comets, long-period comets, trans-Neptunian objects, and
asteroids were considered. The total probability of collisions of any
considered body or particle with all planets did not exceed 0.2. The amount of
water delivered from outside of Jupiter's orbit to the Earth during the
formation of the giant planets could exceed the amount of water in Earth's
oceans. The ratio of the mass of water delivered to a planet by Jupiter-family
comets or Halley-type comets to the mass of the planet can be greater for Mars,
Venus, and Mercury, than that for Earth.
