Integration of the Clementine UV‐VIS spectral reflectance data and the Lunar Prospector gamma‐ray spectrometer data: A global‐scale multielement analysis of the lunar surface using iron, titanium, and thorium abundances

Abstract

[1] We present a statistical analysis, based on a systematic clustering method, of a data set integrating the global abundances maps of iron, titanium, and thorium derived from Clementine and Lunar Prospector. Homogeneous geological units are compositionally characterized and spatially defined in relation to the major rock types sampled on the Moon. With the lowest abundances in Fe, Ti, and Th found on the Moon, the lunar highlands terrains are quite homogeneous with two major large feldspathic units, one being slightly more mafic than the other. Two distinct regions with unique compositions are unambiguously identified: the Procellarum KREEP Terrane (PKT) and the South PoleAitken (SPA). The PKT, which includes all the units with Th abundances higher than 3.5 ppm (KREEP-rich materials), is delimited by an almost continuous ring-like unit. In particular, it includes the western nearside maria, except for Mare Humorum. Within the PKT a Th-rich unit, corresponding to the highest Th concentrations found on the Moon, may represent KREEP volcanic deposits excavated from relatively shallow depth. With concentrations in Fe, Ti, and Th enhanced relative to the surrounding highlands, the South Pole-Aitken basin floor represents a large mafic anomaly on the farside, suggesting wide deposits of lower crust and possible mantle materials. However, due to indirect residual latitude effects in the Clementine spectral reflectance measurements, iron abundances might have been overestimated in SPA, thus implying that crustal materials, rather than mantle materials, might represent the dominant contributor to the mafic component exposed on the basin floor.

Petrogenesis of picritic mare magmas: Constraints on the extent of early lunar differentiation

“…sion of heat flow data, noting that the two mare sites where the measurements were taken probably were underlain by anomalously conductive crust. In light of the Clementine (Chevrel et al, 2002) and Prospector Lawrence et al, 2000) data showing the enrichment of Th (and thus presumably U) in the PKT terrane (Jolliff et al, 2000), it is clear that heat flow in this region, which includes the sites where the measurements were made, is expected to be higher than average surface values. Thus the inverted bulk Moon Th and U concentrations are likely to be too high and, likewise, the concentrations of the other refractory elements estimated by Taylor (1982) are likely to be too high, as well.…”

Remote laser‐induced breakdown spectroscopy (LIBS) for lunar exploration

“…Goals of renewed exploration include understanding of how the Moon differentiated, the nature of its interior, and the stratigraphy of the lunar crust [ NRC , 2007]. It has been suggested that the SPA Basin, and potentially other large impact basins, can be used to address these questions, as during their formation they may have excavated through the lunar crust, exposing upper mantle lithologies [ Pieters et al , 2001; Chevrel et al , 2002].…”

Iron abundances on the lunar surface as measured by the Lunar Prospector gamma‐ray and neutron spectrometers

“…While the scope of this paper does not allow a detailed investigation of how all these techniques compare, it will be helpful to make a few comments about the eventual integration of these data sets. Specifically, as pointed out by Clark and McFadden [2000], Lucey et al [2000], Chevrel et al [2002], and others, these data sets are complementary and by combining the information from each data set, more information about global iron abundances and other chemical characteristics of the lunar surface will certainly be obtained than could be derived from each data set alone.…”