  Nitrogen, carbon monoxide, and methane are key materials in the far outer
Solar System where their high volatility enables them to sublimate, potentially
driving activity at very low temperatures. Knowledge of their vapor pressures
and latent heats of sublimation at relevant temperatures is needed to model the
processes involved. We describe a method for using a quartz crystal
microbalance to measure the sublimation flux of these volatile ices in the free
molecular flow regime, accounting for the simultaneous sublimation from and
condensation onto the quartz crystal to derive vapor pressures and latent heats
of sublimation. We find vapor pressures to be somewhat lower than previous
estimates in literature, with carbon monoxide being the most discrepant of the
three species, almost an order of magnitude lower than had been thought. These
results have important implications across a variety of astrophysical and
planetary environments.
