What avg density [kg/m^3] may I attribute to solar system space dust? Halliday & Resnick give E-18 to E-21 [kg/^3]. This will allow me to compute solar system density, if I know solar system radius[m], ie, distance from edge of solar system to centre-of-mass of our Sun. By 'space dust' I mean any mass, not found within our Sun and its planets. This would include moons, comets, asteroids. If you can give me the total mass and volume of the moons in our solar system, then I will alter my definition of space dust to mean any mass, not found within our Sun, moons, and suns planets.