MIGRATION OF DUST PARTICLES AND VOLATILES DELIVERY TO THE INNER PLANETS. M. Ya. Marov, M.V. Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, Miusskaya sq. 4, Moscow 125047, Russia (marov@spp.keldysh.ru), S. I. Ipatov, University of Maryland, USA (siipatov@hotmail.com). Introduction. Delivery of volatiles by small bod- ies to the terrestrial planets in terms of formation and evolution of their atmospheres/hydrospheres was earlier discussed by us [1-4]. We shall now address the role of dust particles in such a delivery. Particulate matter is produced by comets, trans-Neptunian objects, and as- teroids. These interplanetary dust particles (IDPs) mi- grate in the Solar System and can collide with terres- trial planets, some trans-Neptunian objects getting first Jupiter-crossing orbits. Our results of computer sim- ulations showed [5-6] that a small fraction of Jupiter- crossing objects (JCOs) can transit to the orbits typical for near-Earth objects and even to typical asteroid or- bits, and some of them reside such orbits for tens or even hundreds of millions years. One may thus assume that many former comets composed mainly of late conden- sates and carbonaceous chondrites and closely related to trans-Neptunian objects, disintegrated inside Jupiter’s orbit during this long period of time giving rise to enor- mous amount of dust particles of primordial origin. In pursuit of these basic ideas, migration of dust particles from different regions of the solar system was numeri- cally integrated [7-8]. In evaluating asteroid and trans- Neptunian particles migration, we started from num- bered main-belt asteroids and known trans-Neptunian objects, whereas comets 2P Encke and 10P Tempel 2 were selected as representative source of comet debris production. The refined model will be discussed with the goal to evaluate a potential contribution of dust par- ticles in the delivery of volatiles to the terrestrial planets. Results of the modeling. Collision probability with the Earth of dust particles with genesis to aster- oids was found [7-8] to have a maximum ( 0.001-0.02) at 0.002 0.01 (where is the ratio of the radia- tion pressure to the gravitational force and is a value for one particle), i.e., for the particle diameters 100 m. This is in accordance with cratering records in the lunar soil and also with particles record on the panels of the Long Duration Exposure Facility, which showed that the mass distribution of dust particles encountering Earth peaks at =200 m. For Venus values didn’t differ much from those for Earth, whereas for Mars they were by an order of magnitude smaller at 0.01 com- pared to Earth, and nearly similar to those for Earth at 0.0004-0.001. Collision probability with terrestrial planets of the Comet 10P dust debris, was found to be only a few times different compared to that for particles generated by as- teroids. In turn, for Comet 2P dust debris, the values were found usually smaller than for asteroid and comet 10P particles: for Earth at 0.002 0.01, were by an order of magnitude smaller for 2P particles than for asteroid particles. For 2P particles at some , is by the factor of 2 or 4 greater for Venus than for Earth. Collision probabilities of trans-Neptunian parti- cles with Earth and Venus at 0.01 were and were usually less than those for asteroid particles by the factor of less than 4. Another source of interest is interstellar particles tran- siting the planetary system with hyperbolic velocities and becoming increasingly important beyond 3 AU from the Sun where they appear to dominate micron- and submicron-sized interplanetary dust. Direct col- lisions of these particles with terrestrial planets is ex- pected to be negligible. However, interstellar particles can be effective in destruction of trans-Neptunian dust particles through collisions, especially with grains be- tween 9 m and 50 m, as it is argued in [9]. Larger particles may survive because interstellar grains are too small to destroy them in a single impact. Since the total mass of the trans-Neptunian belt exceeds that of the asteroid belt by more than two orders of magnitude, and the derived in our model mean residence times ratio in orbits with perihelion distance 1 AU for asteroid and trans-Neptunian particles is less than 20 at 0.05, then for 1-10 m the fraction of trans-Neptunian dust of the overall dust population can be significant even at 3 AU. These particles should not be icy, how- ever, because they easily evaporate when approaching the near-Earth and other inner planets space [9]. Volatiles Delivery. It is reasonably assumed that collisional interaction of planetesimals resulted in enor- mous dust production in due course of the planets for- mation. Numerous planetesimals from the zone beyond Jupiter’s orbit resided Jupiter-crossing orbits which could be similar to the orbits of Jupiter-family comets, with their follow up disintegration and/or migration inward the solar system. It was earlier shown [2-6] that even a relatively small portion ( 0.001) of JCOs which transit to orbits with aphelia inside Jupiter’s orbit ( 4.7 AU) and reside such orbits during more than 1 Myr may contribute sig- nificantly in collisions with the terrestrial planets and thus deliver significant amount of volatiles. Assuming that the mean collision probability of JCOs with Earth is and the total mass of planetesi- Lunar and Planetary Science XXXVI (2005) 1268.pdf