Science Concept 2: The Structure and Composition of the Lunar Interior Provide Fundamental Information on the Evolution of a Differentiated Planetary Body

Each of the Science Goals addressed by Science Concept 2 is linked: data regarding the crust, mantle, and core must be obtained in order to understand the thermal state of the interior and the planetary heat engine. Much about these Science Goals is currently unknown: crustal thickness and lateral variability are constrained by gravity and seismic models which suffer from non-uniqueness and a lack of control points; mantle composition is ambiguously estimated from seismic velocity profiles and assumed lunar bulk compositions; mantle structure is obtained through seismic velocity profiles, but fine-scale structure is not resolved and any structure outside the Apollo network and below 1000 kilometers depth is unknown; the size, composition and state of the core are obtained through models with few constraints, where the size and state are dependent on an unknown composition, making any core characteristic estimates highly variable; and the thermal state of the interior is constrained by heat flow measurements and characteristics of the core, but current heat flow data are not representative of the global heat flux and core models are non-unique. Besides elucidating the principle objectives of each Science Goal, addressing this Science Concept will also provide data regarding formation and evolution models of the Moon (i.e., the Giant Impact (e.g., Canup, 2004a, 2004b) and Lunar Magma Ocean (LMO; e.g., Wood et al., 1970) hypotheses, the details of which are debated or unknown.