This paper examines both Triton's atmospheric escape rates and radiative timescales.

We first calculate the range of plausible atmospheric escape rates and examine the implications of these escape fluxes. If even modest hydrodynamic escape is occurring, escape rates can exceed the ion pickup rates predicted by Delitsky, et al. (1989). This process is expected to develop a torus of gas in orbit around Neptune. If Triton's escape flux exceeds ~1010 cm-2 sec-1, a substantial amount of ancient icy surface topography may have been lost to escape.

We also calculate the radiative timescale in Triton's atmosphere as a function of surface temperature, atmospheric pressure, and composition. It is shown that if N2 obtains saturation vapor pressure equilibrium, then diurnal variations will be negligible. If N2 is far from saturation or if only CH4 is present, then both diurnal and seasonal effects may be expected. Recent observations indicate the presence of decadal-timescale atmospheric variations. Radiative timescale constraints imply that if these observations are correct, then the present atmospheric pressure is unlikely to much exceed ≈100 mb. ¿ American Geophysical Union 1989