the moon's total thorium amount is hard to pin down precisely due to incomplete mapping, but estimates suggest concentrations of 1-10 ppm in the lunar crust, with highlands richer in thorium than average. this is comparable to earth's continental crust average of about 9.6 ppm, but the moon's highlands show higher enrichment in thorium and similar elements relative to earth's mantle. nasa lunar prospector data. https://ntrs.nasa.gov/citations/20050117585 prettyman et al. (2006) journal of geophysical research. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006JE002723