  Escape of an early atmosphere from Titan, during which time NH3 could be
converted by photolysis into the present N2 dominated atmosphere, is an
important problem in planetary science. Recently Gilliam and Lerman (2014)
estimated escape driven by the surface temperature and pressure, which we show
gave loss rates that are orders of magnitude too large. Their model, related to
Jeans escape from an isothermal atmosphere, was used to show that escape driven
only by surface heating would deplete the atmospheric inventory of N for a
suggested Titan accretion temperature of ~355 K. Therefore, they concluded that
the accretion temperature must be lower in order to retain the present Titan
atmosphere. Here we show that the near surface atmospheric temperature is
essentially irrelevant for determining the atmospheric loss rate from Titan and
that escape is predominantly driven by solar heating of the upper atmosphere.
We also give a rough estimate of the escape rate in the early solar system
(~10^4 kg/s) consistent with an inventory of nitrogen being available over the
time period suggested by Atreya et al. (1978) for conversion of NH3 into N2.
