Origin of fifteen cosmic dust particles intercepted by Pioneer 8 and 9

Consistent data for more than 8 years have been obtained from two identical cosmic dust particle experiments on board the space probes Pioneer 8 and 9. The two spacecraft are in direct heliocentric orbits with perihelia between 0.75 AU and 1.00 AU. On the basis of the data it is concluded that the majority of dust particles having elliptical orbits detected by the two space probes show orbital characteristics of Apollo group asteroids which originated from residual nuclei of short-period comets.