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tokens: flow direction forms with the grain’s velocity. The first part of Eq. ( 9 ) is the sum of radiation pressure force with the corpuscular pressure force split into its radial and transverse component. The latter part of Eq. ( 9 ) is the sum of the classical PR drag with the solar wind drag ( Marzari Vanzani 1994 ). The adopted numerical algorithm for solving the equations of motion is the RA15 version of the RADAU integrator ( Everhart 1985 ). 3. Initial conditions for asteroidal dust and cometary dust particles To compute the flux of dust particles released in the main belt through asteroidal collisions and reaching the Earth and Mercury, we adopted an initial distribution of orbital elements with the following characteristics ( Borin et al. 2009 ; Marzari et al. 1996 ; Dohnanyi 1969 ). The initial semimajor axis is randomly selected in between 2.1 and 3.3 AU, the initial eccentricity varies in the range 0.00.4 and the inclination is in the range . This choice reflects the typical orbital elements of the asteroid belt ( Gradie et al. 1989 ; Zappalá Cellino 1993 ; Zappalá et al. 1994 ; Milani Knezevic 1994 ). We assume a grain density of , which is a reasonable value for dust particles coming from the main belt asteroids ( Grün et al. 1985 ). Spherical particles are considered in the approximation of Mie’s theory for which , the dimensionless, radiation-pressure coefficient averaged over the solar spectrum, is 0.53 ( Marzari Vanzani 1994 ; Mukai et al. 1982 ). For the JFC dust particles we considered orbits with an initial semimajor axis in a range between 2.5 and 26.7 AU with the majority of dust grains in the range between 2.5 and 8 AU, eccentricity in a range interval between 0.3 and 0.9, and orbit inclination in the range between with a large concentration of particles in the range between . In this case, we assume a density of , the radiation pressure coefficient following the asteroids grain simulations ( Marzari Vanzani 1994 ; Mukai et al. 1982 ). The initial orbital elements of comets are taken from Nesvorny et al. (2010) and Levison Duncan (1997) , who followed the evolution of bodies originating in the Kuiper Belt as they are scattered by planets and evolve into the inner solar system. In their input list of source objects, Nesvorny et al. (2010) consider a JFC to become active at the time when the perihelion distance, q first drops below 2.5 AU in the Levison Duncan (1997) simulations. The orbital distribution of visible JFCs obtained with this model by Levison Duncan (1997) well approximates the observed distribution. Defining as the fading lifetime of JFCs, which is the time range between their first and last appearance ( Levison Duncan 1997 ; Nesvorny et al. 2010 ), we considered both the initial time and the final time () for each comet with perihelion distance . However, the outcome in terms of close encounters and impact speed was not significantly different, so we used the set with the final time. In Fig. 1 we illustrate the