Remote sensing and geological studies of the Hadley-Apennine region of the Moon

Abstract

We have used data from the Clementine and Lunar Prospector spacecraft in conjunction with reflectance spectra collected with Earth-based telescopes to study the geology of the Hadley-Apennine portion of the lunar Imbrium basin. The Apennine Mountains and the Imbrium backslope are composed of Imbrium basin ejecta with a noritic or anorthositic norite composition. We find that the two major facies of Imbrium ejecta, the Apenninus material and the Alpes Formation, differ in iron and titanium content. "Pure" anorthosite has tentatively been identified in the ejecta of the crater Conon, based on low-iron content. A difference in Th and rare earth element (REE) abundance between the northeast Apennine Mountains (lower) and the southwest Apennines (higher) is noted Pyroclastic deposits are common in the region and are dominated by mare basalt material, probably plug rock ejected in vulcanian eruptions. The Apennine Bench Formation, which is likely to be a deposit of non-mare volcanic material, has an Fe, Ti and Th composition consistent with that of Apollo 15 KREEP basalt samples thought to be fragments of the Bench. Aristillus crater is a Th and REE hot spot, and the stratigraphy of the impact target site has been reconstructed from knowledge of the composition of the crater interior and exterior deposits. We infer that the target consisted of highland basement, KREEP plutonics and volcanics, and both high- and low-Ti mare basalt.