The gateway from Centaurs to Jupiter-family Comets: thermal and dynamical evolution

TL;DR

This study investigates the 'gateway' in orbital space through which Centaurs become Jupiter-family Comets, revealing that gateway objects are more thermally processed and often not pristine progenitors, with over half having prior JFC history.

Contribution

The paper demonstrates that most gateway Centaurs are thermally processed and not pristine, and that a significant portion of JFCs have previously passed through the gateway or avoided it initially.

Findings

Over 50% of JFCs have already been thermally processed before reaching the gateway.

Only about 20% of Centaurs pass through the gateway before becoming JFCs.

Many JFCs have prior history as JFCs, not just newly arriving from Centaurs.

Abstract

It was recently proposed that there exists a "gateway" in the orbital parameter space through which Centaurs transition to Jupiter-family Comets (JFCs). Further studies have implied that the majority of objects that eventually evolve into JFCs should leave the Centaur population through this gateway. This may be naively interpreted as gateway Centaurs being pristine progenitors of JFCs. This is the point we want to address in this work. We show that the opposite is true: gateway Centaurs are, on average, more thermally processed than the rest of the population of Centaurs crossing Jupiter's orbit. Using a dynamically-validated JFC population, we find that only $\sim 20\%$ of Centaurs pass through the gateway prior to becoming JFCs, in accordance with previous studies. We show that more than half of JFC dynamical clones entering the gateway for the first time have already been JFCs -they simply avoided the gateway on their first pass into the inner solar system. By coupling a thermal evolution model to the orbital evolution of JFC dynamical clones, we find a higher than 50\% chance that the layer currently contributing to the observed activity of gateway objects has been physically and chemically altered, due to previously sustained thermal processing. We further illustrate this effect by examining dynamical clones that match the present-day orbits of 29P/Schwassmann-Wachmann 1, P/2019 LD2 (ATLAS), and P/2008 CL94 (Lemmon).