Permanently shaded regions of the lunar poles may constitute one of the important sinks for volatiles. Lunar Prospector showed excesses of hydrogen at the 50 km to 100 km scale near the poles, although radar detects no widespread thick deposits of volatiles (unlike at the poles of Mercury). Despite the fact that these cold, shadowed surfaces are expected to act as lunar cold traps, their effectiveness in trapping volatiles for long periods is unknown. Regardless of total efficiency, the lunar polar soil may contain a wealth of scientific information on solar system volatiles.
Significant gaps remain in the understanding of the lunar atmosphere system, especially the three-dimensional flows and nature of constituents through the atmosphere, the detailed behavior of dust and its relationship to the vapor component, and the role and state of the polar cold traps. It is safe to say that the dynamic system exists, but there is no predictive understanding of its behavior.
The more than 30 years since the Apollo program have enabled lunar and other scientists to make great strides in the understanding of the origin and evolution of the Moon, Earth, and other planets using the Moon as a lens. But this era has also revealed troubling defects in that lens owing to the lack of key data in time, space, and physical characteristics. Building on the foundation of the Apollo program and over 30 years of contemplation and technical progress, a well-formulated new era of lunar exploration will enable key tests of hypotheses major and minor that may revolutionize the understanding of the origin and evolution of the Moon, Earth, and the planets.