Abstract
The measurements of cosmic interplanetary dust by the instruments on board the Pioneer 10 and 11 spacecraft contain the dynamical signature of dust generated by Edgeworth-Kuiper belt objects, as well as short-period Oort cloud comets and short-period Jupiter-family comets. While the dust concentration detected between Jupiter and Saturn is mainly due to the cometary components, the dust outside Saturn's orbit is dominated by grains originating from the Edgeworth-Kuiper belt. In order to sustain a dust concentration that accounts for the Pioneer measurements, short-period external Jupiter-family comets, on orbits similar to that of comet 29P/Schwassmann-Wachmann 1, have to produce 8 × 104 g s-1 of dust grains with sizes between 0.01 and 6 mm. A sustained production rate of 3 × 105 g s-1 has to be provided by short-period Oort cloud comets on 1P/Halley-like orbits. The comets cannot, however, account for the dust flux measured outside Saturn's orbit. The measurements there can only be explained by generation of dust grains in the Edgeworth-Kuiper belt by mutual collisions of the source objects and by impacts of interstellar dust grains onto the objects' surfaces. These processes have to release in total 5 × 107 g s-1 of dust from the Edgeworth-Kuiper belt objects in order to account for the amount of dust found by Pioneer beyond Saturn, making the Edgeworth-Kuiper disk the brightest extended feature of the solar system when observed from afar.