Evolution of Cometary Dust Particles to the Orbit of the Earth: Particle Size, Shape, and Mutual Collisions

TL;DR

This study numerically examines the orbital evolution of cometary dust particles, highlighting planetary encounters as the main factor affecting their lifetimes and distribution, with implications for understanding the interplanetary dust environment.

Contribution

It provides the first direct numerical estimation of mutual collision probabilities among dust particles in the interplanetary dust cloud.

Findings

Planetary encounters, especially with Jupiter, dominate dust particle orbital evolution.

Dust particle lifetimes are around 250,000 years, shorter than Poynting-Robertson timescale.

Mutual collisions among dust particles are generally negligible.

Abstract

In this study, we numerically investigated the orbital evolution of cometary dust particles, with special consideration of the initial size frequency distribution (SFD) and different evolutionary tracks according to initial orbit and particle shape. We found that close encounters with planets (mostly Jupiter) are the dominating factor determining the orbital evolution of dust particles. Therefore, the lifetimes of cometary dust particles (~250 thousand years) are shorter than the Poynting-Robertson lifetime, and only a small fraction of large cometary dust particles can be transferred into orbits with small values of a. The exceptions are dust particles from 2P/Encke and, potentially, active asteroids that have little interaction with Jupiter. We also found that the effect of dust shape, mass density, and SFD were not critical in the total mass supply rate to the Interplanetary Dust Particle (IDP) cloud complex when these quantities are confined by observations of zodiacal light brightness and SFD around the Earth's orbit. When we incorporate a population of fluffy aggregates discovered in the Earth's stratosphere and the coma of 67P/Churyumov-Gerasimenko within the initial ejection, the initial SFD measured at the comae of comets (67P and 81P/Wild 2) can produce the observed SFD around the Earth's orbit. Considering the above effects, we derived the probability of mutual collisions among dust particles within the IDP cloud for the first time in a direct manner via numerical simulation and concluded that mutual collisions are mostly ignorable.