  Evidence for cometary activity beyond Jupiter and Saturn's orbits -- such as
that observed for Centaurs and long period comets -- suggests that the thermal
processing of comet nuclei starts long before they enter the inner Solar
System, where they are typically observed and monitored. Such observations
raise questions as to the depth of unprocessed material, and whether the
activity of JFCs can be representative of any primitive material. Here we model
the coupled thermal and dynamical evolution of Jupiter Family Comets (JFCs),
from the moment they leave their outer Solar System reservoirs until their
ejection into interstellar space. We apply a thermal evolution model to a
sample of simulated JFCs obtained from dynamical simulations (arXiv:1706.07447)
that successfully reproduce the orbital distribution of observed JFCs. We show
that due to the stochastic nature of comet trajectories toward the inner solar
system, all simulated JFCs undergo multiple heating episodes resulting in
significant modifications of their initial volatile contents. A statistical
analysis constrains the extent of such processing. We suggest that primordial
condensed hypervolatile ices should be entirely lost from the layers that
contribute to cometary activity observed today. Our results demonstrate that
understanding the orbital (and thus, heating) history of JFCs is essential when
putting observations in a broader context.
