Comet Fading Begins Beyond Saturn
  The discovery probability of long-period comets (LPCs) passing near the Sun
is highest during their first passage and then declines, or fades, during
subsequent return passages. Comet fading is largely attributed to
devolatilization and fragmentation via thermal processing within 2-3 au of the
Sun (1 au being the Earth-Sun distance). Here our numerical simulations show
that comet observing campaigns miss vast numbers of LPCs making returning
passages through the Saturn region (near 10 au) because these comets fade
during prior, even more distant passages exterior to Saturn and thus elude
detection. Consequently, comet properties significantly evolve at solar
distances much larger than previously considered, and this offers new insights
into the physical and dynamical properties of LPCs, both near and far from
Earth.
