Water and Volatiles as Tracers of Lunar Formation, Differentiation, and Bombardment
Jeff Taylor

After decades of being thought to be virtually completely lacking in water, we now know that the Moon contains H2O in its interior. Based on analyses of a variety of rocks, water is not distributed uniformly throughout the interior. Why is water not uniform in abundance? How much is there in total compared to Earth and other terrestrial planets? Where did the water come from? Addressing these questions requires that we probe into how the Moon formed, how it solidified from an initially molten state, and whether water was added after the Moon formed. Processes in the proto-lunar disk surrounding the Earth might or might not lead to substantial water loss. The patchy water distribution might simply reflect how the Moon crystallized as it cooled from an initial mostly molten state (the Moon's primary differentiation). Or perhaps water was added after the Moon had finished its primary differentiation-perhaps large water-bearing impactors crashed into the Moon, distributing their water heterogeneously deep in the interior. I'll explore these options. Don't expect definitive answers.