Dispersal of gases generated near a lunar outpost

The extremely low density of the present lunar atmosphere provides an ideal environment for activities such as high-vacuum materials processing and high resolution astronomy. The aim of this work is to study the dispersal of gases arising from operations on a future lunar outpost and to predict its effects on these activities. The dispersal is modeled analytically using continuous (e.g., mining and habitat venting) and impulsive (e.g., rocket exhaust) injection mechanisms and assuming a collisionless, isothermal atmosphere. In the impulsive injection case, the neutral atmosphere and associated ionosphere both decay on time scales of about 20 min. In the continuous injection scenario, the atmosphere near the outpost grows and reaches a steady state after approximately 20 min. For a moderate injection rate (1 kg/s), any significant atmosphere is limited to within 1 km of the source. The resulting ionosphere impacts radio astronomical observations only within 10 km of the source. Both direct transport and diffusive transport (i.e., repeated bounces off of the lunar surface) are considered. It is concluded that at these injection rates and within the constraints of our assumptions, an artificial lunar atmosphere is not a serious detriment to astronomical observations and high-vacuum materials processing.