Present‐Day Thermal State and Surface Heat Flux of the Moon

Kurzfassung

The concentration of volcanic material and Heat-Producing Elements (HPE) on the lunar nearside surface suggests an asymmetry of interior properties and thermal history between the two hemispheres. However, the distribution of HPE beneath the surface and the processes that led to their potential enrichment on the nearside remain poorly understood. Here, we use a 3D geodynamic model to infer the interior distribution of HPE based on surface heat flux estimates. We explore the consequences of a putative HPE-rich unit underneath the Procellarum region on the lateral variations of the present-day surface heat flux. Assuming a circular geometry and 1.6 km average thickness, we explore various sizes, locations, and enrichments of the HPE-rich unit, including the complete absence of such an anomaly, and select successful scenarios based on models that match the Apollo heat flux measurements. Scenarios with either a homogeneous HPE distribution in the mantle or a globally uniform HPE-rich layer lead to surface heat fluxes inconsistent with Apollo data. Conversely, a HPE anomaly beneath the nearside, extending at least to the Apollo 15 landing site and at most encircling the entire mare region, including Apollo 17 landing site, can match both measurements. The required Th concentration within the anomaly ranges from 23 to 50 ppm, assuming a 1.6 km thickness. Finally, we predict heat flux ranges of 7–12 mW/ and 8–14 mW/ for the upcoming Blue Ghost Mission 1 and APEX®1.0 heat flux measurements.