Chaotic Transport and Chronology of Complex Asteroid Families

TL;DR

This paper introduces a stochastic transport model to estimate the ages of complex asteroid families by simulating their orbital diffusion in chaotic regions, incorporating thermal effects like Yarkovsky/YORP.

Contribution

It develops a simple random-walk model with diffusion coefficients and drift to accurately estimate asteroid family ages, validated on known and older families.

Findings

Successfully estimated the age of the Veritas family (~8.3 Myr).

Estimated the age of the Lixiaohua family as 155±36 Myr.

Reproduced the spreading of family members in proper elements space.

Abstract

We present a transport model that describes the orbital diffusion of asteroids in chaotic regions of the 3-D space of proper elements. Our goal is to use a simple random-walk model to study the evolution and derive accurate age estimates for dynamically complex asteroid families. To this purpose, we first compute local diffusion coefficients, which characterize chaotic diffusion in proper eccentricity (e_p) and inclination (I_p), in a selected phase-space region. Then, a Monte-Carlo-type code is constructed and used to track the evolution of random walkers (i.e. asteroids), by coupling diffusion in (e_p,I_p) with a drift in proper semi-major axis (a_p) induced by the Yarkovsky/YORP thermal effects. We validate our model by applying it to the family of (490) Veritas, for which we recover previous estimates of its age (~8.3 Myr). Moreover, we show that the spreading of chaotic family members in proper elements space is well reproduced in our random-walk simulations. Finally, we apply our model to the family of (3556) Lixiaohua, which is much older than Veritas and thus much more affected by thermal forces. We find the age of the Lixiaohua family to be 155+/-36 Myr.