Lunar farside Th distribution measured by Kaguya gamma-ray spectrometer

Kaguya gamma-ray spectrometer measured thorium (Th) distribution on the lunar farside with the highest sensitivity among past gamma-ray remote sensing missions. The newly obtained Th map has revealed that two regions near the equator on the farside have the lowest Th abundances. We found that the variation of the Th abundance perfectly correlates with the crustal thickness in the farside and the southern nearside, and it could be a result of the crystallization of the lunar magma ocean.

► Kaguya gamma-ray spectrometer accurately measured Th distribution of the lunar surface.
► We found that the two regions near the equator on the farside have the lowest Th abundances.
► We found the perfect correlation between the Th abundance and the crustal thickness.
► The correlation could be vestige of the crystallization of the lunar magma ocean.