Remote sensing and geochemical constraints on asteroid and lunar composition

This dissertation is comprised of three parts concerned with aspects of asteroid or lunar composition. In Part I, a spectral model for asteroid surfaces based on Hapke's radiative transfer theories incorporating an improved treatment for the spectral properties of coarse-grained iron-nickel metal (CGM) is presented. The spectral effects of enhanced CGM abundances are found to be similar to those of submicroscopic iron in some situations. The class and petrologic type of predicted ordinary chondrite parent bodies are found to have a minor spectral effect.; In Part II, the geochemical anomaly northeast of Dewar crater, a low-albedo area with enhanced Th and Sm values and elevated FeO and TiO2 abundances, is investigated. Clementine spectra indicate that these low-albedo materials contain large amounts of high-Ca pyroxene consistent with the presence of buried mare basalt, or cryptomare. An early Imbrian- or Nectarian-age, low-TiO 2 mare basalt deposit with enhanced Th concentrations (6--7 mug/g) exists in the Dewar region and was excavated during subsequent impact events, creating the geochemical anomaly. Mare units on the central far side of the Moon generally exhibit low Th abundances, but enhanced Th values associated with the Dewar cryptomare deposit indicate portions of the lunar interior on the far side were not Th-poor.; Lunar samples 72435, 76315, 76295, and 76035 are impact melt breccias containing relict mineral fragments from rocks located near the Serenitatis basin-forming impact and subsequently incorporated into the impact melt, offering insights into the composition of the lunar crust in the Serenitatis region. Electron microprobe analysis and laser-ablation inductively-coupled plasma mass spectroscopy were utilized to collect geochemical data from 122 olivine, pyroxene, and plagioclase mineral fragments. 12% of the analyzed plagioclase fragments are ferroan anorthosite materials, confirming their presence in the Serenitatis crustal section. The remaining fragments are primarily Mg-suite materials. Many of the fragments have trace element concentrations unlike previously described primary igneous lunar highlands materials, indicating that the pre-impact Serenitatis crust was heterogeneous and composed of rocks from several magma sources.