Exogenic dust inventory in the Saturn system: the Cassini Cosmic Dust Analyzer perspective

Abstract

We constrain the inventory of exogenic dust populations found in the Saturn system by analysing 14 yr of Cassini Cosmic Dust Analyzer (CDA) data acquired since Saturn orbit insertion. Our analysis reveals that the Saturn system is permanently traversed by exogenic dust coming from the surrounding interplanetary space, interplanetary dust particles (IDPs), and from the interstellar medium, interstellar dust (ISD). The CDA data give a first in situ experimental insight into the different dust populations of the outer Solar system and their relative abundances. We observe a population of sub-micron to tens of micron-sized interplanetary grains, with low injection speed at Saturn’s Hill’s boundary, and whose dynamical signature supports their collisional origin in the Edgeworth Kuiper belt or a release upon cometary activity of Jupiter-family comets and Centaurs. We confirm that those populations are the most abundant IDP population in the Saturn system, participating to the weathering of the surfaces of the icy moons and the rings. We also observe the signature of sub-micron grains with high injection speeds at Saturn’s Hill’s radius, bearing the dynamical signature of dust released by Oort cloud comets. In addition, a population of large ISD grains appears clearly in our data, in the micrometre-sized regime, hence larger than detected in situ by previous missions and analysis. Finally, we also find hints of an extended dust halo of bound particles, reaching high latitudes in the inner Saturn system as well as possible sporadic sources of interplanetary grains.