A DYNAMICAL-PHYSICAL EVOLUTION MODEL FOR JUPITER-FAMILY COMETS AND CENTAURS

MARIO NASCIMENTO DE PRÁ; LUKE DONES; MARIA WOMACK; DAVID NESVORNÝ; ROMINA P. DI SISTO

Congreso; 53 Anual meeting of the Division for Planetary Sciences of AAS; 2021

The Cassini-Huygens mission imaged the saturnian moons at fine resolution, enabling the Measurement of impact craters with diameters ranging from less than 1-km to many hundreds of km [1, 2]. Relative surface ages can be estimated based on superposition relationships, relative crater spatial densities. Inferring absolute ages requires a model for the impactor flux and a crater scaling relationship [3, 4, 5, 6]. As part of an effort to interpret the cratering records of the saturnian moons, we are developing a dynamical-physical model for the size distribution of potential impactors on the moons. The primary source of impactors is likely Centaurs, most of which originate from the Kuiper Belt/Scattered Disk. In order to build a realistic model for the impact flux onto the saturnian moons, we must consider the physical evolution of these objects. Some Centaurs display cometary activity at distances beyond Saturn?s orbit [7], notably 174P/Echeclus, which underwent a large outburst at 13 au from the Sun [8]. Di Sisto et al. (2009) proposed a dynamical-physical model for Jupiter-family comets (JFCs) [9], which included the effects of planetary perturbations, and nongravitational forces, such as caused by sublimation of volatiles, and splitting. Inspired by their work, we are developing a model for the dynamical-physical evolution of JFCs and Centaurs. We will use the orbital distribution from Nesvorný et al. (2017) as our baseline dynamical model [10], and eventually account for mass loss by both JFCs and Centaurs, with activity driven by H2O, CO, or other volatiles. The fraction of the nucleus that is active will be allowed to vary with size, since smaller nuclei are typically more active [11]. Finally, we will implement a model for cometary splitting that considers the frequency of splitting as a function of perihelion distance; the fraction of the comet?s mass released as fragments; the size distribution of the fragments; and the velocity imparted to the fragments by the splitting event. We will present preliminary results of our simulations. We thank the NASA Cassini Data Analysis Program for support. References: [1] Kirchoff, et al., Enceladus and the Icy Moons of Saturn, pp. 267-284, 2018. [2] Ferguson, et al, JGR Planets 125, e06400, 2020. [3] Zahnle, et al., Icarus 136, 202?222, 1998. [4] Zahnle, et al., Icarus 163, 263?289, 2003. [5] Di Sisto & Zanardi, Icarus 264, 90?101,2016. [6] Rossignoli, et al., A&A 627, A12, 2019. [7] Jewitt, AJ 137, 4296?4312, 2009. [8] Rousselot, A&A 480, 543-550, 2008. [9] Di Sisto, et al., Icarus 203, 140?154, 2009. [10] Nesvorný, et al., ApJ 845, 27, 2017. [11] Tancredi, et al., Icarus 182, 527?549, 2006.