Unveiling Basalt Distribution of Lunar Cryptomaria from Gravity and Topography when Considering the Effect of Surface Cover-layer and Density Correction

Abstract The cryptomaria preserves critical evidence of early lunar volcanism and thermal evolution, offering key constraints on the Moon’s internal heat flow and mantle melting processes. To better constrain the distribution of cryptomaria basalt, we present a three-layer density-structure model incorporating contributions from a surface cover-layer, basalt, and underlying anorthositic crust. First, we explicitly account for the effect of the surface cover-layer. Second, to realistically capture nonlinear variation within the anorthositic crust, we apply a Gaussian correction term to adjust the nonlinear component, thereby more accurately modeling density variation. Finally, by utilizing the effective density spectrum derived from Gravity Recovery and Interior Laboratory gravity and Lunar Reconnaissance Orbiter Laser Altimeter topographic data, we estimate the global average thickness of cryptomaria basalts to be approximately 0.54 km, which is notably greater than previous estimates (∼0.40 km) that did not account for the presence of a surface cover-layer and the Gaussian correction. Furthermore, based on the revised thickness distribution, we estimate the total volume of cryptomaria to be ∼4.7 × 10 6 km 3 , a value comparable to that of the visible mare, highlighting the significant contribution of buried basaltic deposits to the Moon’s volcanic activity. Our findings suggest that the traditional model can lead to an underestimation of basalt thickness and volume. The result further indicates a modest negative correlation between basalt and crustal thickness, suggesting that variations in crust alone cannot fully account for the distribution. This finding implies that additional factors—such as mantle thermal heterogeneity and tectonic processes—may play a substantial role in controlling magma emplacement.