The effect of a water-ice mantle on dust trajectories in the Kuiper belt

Abstract

The New Horizons spacecraft has travelled through the Solar System and has reached a distance of 55 AU as of 2023. For one of the first times, the dust flux in the outer Solar System has been measured, using the instrument Student Dust Counter (SDC) onboard New Horizons. Between 30 and 50 AU is the Kuiper belt, which is a disk consisting of icy objects. These objects can undergo collisions, causing them to fragment and generate smaller objects, such as dust grains. The SDC measurements reveal that the dust flux around 50 AU is higher than predicted, indicating that Kuiper belt dust extend beyond the edge of the Kuiper belt. This thesis aims to investigate the behaviour of dust grains that originate in the Kuiper belt, and the extension of the dust ring that these grains form, in order to explain the measurements conducted by SDC. A central aspect of this investigation is to explore the behaviour of water-ice in the Kuiper belt. Simulations of dust grain trajectories that are released from parent objects in the Kuiper belt are performed. The simulations consider grains that are composed of only silicate, and grains that have a mixed composition of silicate and water-ice. An important process that affects the dust is mass loss due to photosputtering, where photons collide with a grain causing the material to erode. For the first time in this thesis, the photosputtering rate is calculated for water-ice grains in the Solar System. The results reveal that the presence of water-ice on Kuiper belt dust significantly influences the orbits of the grains, resulting in a more stable and confined dust ring in the Solar System, with distributions remaining closer to the parent objects compared to the pure silicate grains. However, it is seen that grains originating at approximately 43 AU have orbits that extend beyond the edge of the Kuiper belt, suggesting that dust grains observed beyond 50 AU can be Kuiper belt dust.