So what does all this mean? I suggest that one or more of the existing lines of evidence is giving us misleading information: either the remotely sensed compositional data for basin ejecta, the GRAIL crustal thickness estimates, or the results of the computer impact models are wrong. I list the preceding in order of their likely verity, which also happens to be in order of their closeness to objective measurement and observation. There is a recent tendency in science to place the value of studies in an order reverse to what I have done. Models have taken precedence over observation in many fields, a perverse attitude that turns empiricism on its head and where the “elegance” of a mathematical model is preferred over some inconvenient, observable fact.
Science is constantly revising its corpus of knowledge and today’s “rational consensus” can be tomorrow’s superstitious nonsense. This debate about the nature of the lunar mantle clearly shows the cracks and fault lines in our understanding. Work will continue to map basin deposits in search of excavated deep materials – such features are still one of our best bets to sample and understand the deep lunar interior. As you hear about the results of these studies in the coming years, keep a skeptic’s eye on claims of revolutionary, new interpretations. Such ideas come and go, but knowledge should always be testable and constrained by observations and facts.