Clarissa Family Age from the Yarkovsky Effect Chronology

TL;DR

This study estimates the age of the Clarissa asteroid family at approximately 56 million years by modeling the Yarkovsky effect and planetary perturbations, providing a novel application of this chronology to a young asteroid family.

Contribution

It is the first successful application of Yarkovsky effect chronology to an asteroid family younger than 100 million years, refining age estimation methods.

Findings

Estimated Clarissa family age: 56±6 million years.

Best fit with initial ejection velocities < 20 m/s.

Assumed 80% retrograde initial spins and YORP spin-up preference.

Abstract

The Clarissa family is a small collisional family composed of primitive C-type asteroids. It is located in a dynamically stable zone of the inner asteroid belt. In this work we determine the formation age of the Clarissa family by modeling planetary perturbations as well as thermal drift of family members due to the Yarkovsky effect. Simulations were carried out using the Swift-rmvs4 integrator modified to account for the Yarkovsky and Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effects. We ran multiple simulations starting with different ejection velocity fields of fragments, varying proportion of initially retrograde spins, and also tested different Yarkovsky/YORP models. Our goal was to match the observed orbital structure of the Clarissa family which is notably asymmetrical in the proper semimajor axis. The best fits were obtained with the initial ejection velocities < ~20 m/s of diameter D=2 km fragments, 4:1 preference for spin-up by YORP, and assuming that 80% of small family members initially had retrograde rotation. The age of the Clarissa family was found to be 56+/-6 Myr for the assumed asteroid density 1.5 g/cm3. Small variation of density to smaller or larger value would lead to slightly younger or older age estimates. This is the first case where the Yarkovsky effect chronology has been successfully applied to an asteroid family younger than 100 Myr.