THE MOON Larry Taylor's Group (Research Professors, Visiting Scientists, Postdoctoral Research Associates, and Graduate students) has been studying Lunar Rocks since Apollo 11 first brought samples to Earth in 1969. Their exciting research endeavors have been continuously funded by NASA since that time. The Moon is our nearest celestial neighbor and the only extra-terrestrial object to have been explored by humans. As such, the Moon is our ground truth for exploration of other planets in our Solar System. Although rocks older than 4 billion years old have not been found on Earth, they are abundant on the Moon. Furthermore, current hypotheses of the Moon's origin include those which suggest derivation from Earth. Thus, the Moon may yield clues to Earth's earliest evolution. Mare Basalts All of the basalts collected from the Moon are greater than 3 billion years old and many are extremely well-preserved. Basalts which fill the large basins, or mare ("seas"), on the Moon are direct melts of the lunar interior. The study of these melts yields information on the constitution and evolution of the lunar mantle. Model of ilmenite sinking in the lunar upper mantle over time to generate ilmenite-rich mare basalts over time. (pressure estimates from experimental data) Our research group has been studying the mineralogy, petrology, and chemistry of mare basalts since the Apollo lunar landings over 25 years ago. Radiogenic Isotopic and Geochronologic Studies These mare basalt studies have included analyses of long-lived radiogenic isotopic systems, such as Sm-Nd, Rb-Sr, and recently Lu-Hf, in mare basalts from all landing sites. Sm-Nd whole-rock "isochron" diagram for all Apollo 15, low-Ti mare baasalts. Several quarz-narmative basalts (QNBs) suggest an age of 3.74+_0.12 Ga, whereas others, including several olivine-normative basalts (ONBs) and a picrite suggest a younger age. These analyses have led to a greater understanding of the origin of the Moon and its incipient magma ocean, the age distribution of mare basalts, and the isotopic evolution of the lunar interior. Due to analytical difficulties, the Lu-Hf system has only been used on mare basalts. However, the advent of improved analytical techniques will allow us to analyze two important components in lunar evolution, KREEP basalts, for their Lu-Hf isotopic composition. Lu-Hf isotopic "isochron" diagram for Apollo 15 mare basalts. Most indicate an age of 3.12 Ga, however, sample 15016 projects to lower 176Hf/177Hf along with the Apolo 17 picritic orange glass, 74220. These Lu-Hf studies are performed on the unique multi-collector, magnetic sector, inductively-coupled, plasma-source, mass-spectrometer (MC-MS-ICPMS) housed in the Radiogenic Isotope Geology Laboratory (RIGL) at the University of Michigan. We have also used this instrument to analyze the short lived nuclide 182W in lunar samples. Mineralogy, Petrology, and Mineral Chemistry One of the many strengths of our group is basic mineralogy, petrology, and mineral chemistry of igneous rocks. Although the mineralogy and petrology of most of the large mare basalt samples already have been studied, we are continuing to discover "new" and important mare basalts in the Apollo collections. These samples have added immeasurably to our understanding of the diversity of mare basalts on the near-side of the Moon. Most of the samples returned from the Moon by the Apollo missions are soils and breccias, and included very few, true, basalt rocks. However, careful study of large (1-4 mm) fragments in these soils and breccias, many by our research group, have yielded important new finds of mare basalts. We have recently completed a painstaking search for "new" samples in soils from the Apollo 11 and 12 landing sites. A total of 64 1-4 mm basalt fragments were studied and nearly thirty of these have been classified as pristine, mare basalts. These have included basalts from all known groups, including a rare, Group D, high-Ti basalt from the Apollo 11 landing site Trace-element Chemistry Trace elements have been used to model magmatic processes on the Moon, such as crustal assimilation, partial melting, and fractional crystallization of mantle-derived mare basalts. These studies have allowed us to elucidate the mineralogy and chemistry of upper mantle source regions and their evolution over time, and the nature of surface differentiation processes of mare basalts. For these trace-element analyses, we have used two unique facilities: the High-Flux Isotope Reactor (HFIR) and Neutron-Activation Analysis (NAA) Facility at Oak Ridge National Laboratory and the Inductively-Coupled Plasma Mass-Spectrometry Laboratory at the University of Notre Dame   Ancient Lunar Crust One of the key problems in understanding the origin and evolution of the Moon is determining the age of the earliest lunar crust. This crust is represented by the ferroan anorthosites (FANs), which are believed to be flotation cumulates from an incipient lunar magma ocean (LMO). An understanding of the timing of ferroan anorthosite magmatism will give us information about the age of the crust and the duration of the lunar magma ocean. Chronologies and Isotopic Studies of FANs Several recent isotopic studies have shown the importance of FANs to our understanding of lunar petrogeny. The chronology of FANs suggests a range of ages from 4.57 ± 0.08 Ga to 4.44 ± 0.02 Ga. This age range indicates a need for additional isotopic and geochronologic studies of FANs. Thus, we have begun a Sm-Nd isotopic study of five pristine FAN samples: 62236, 62237, 62255, 62275, and 67215 Ion Probe (SIMS) Analyses of FAN Minerals Trace-element analyses of individual minerals, in concert with known mineral-melt distribution coefficients, should allow one to calculate the liquids from which they crystallized. In order to determine the near-side diversity of FANs, as well as their parental liquids (LMO?), we have begun an ion probe trace-element study of individual minerals in several thin-sections and/or probe-mounts of non-Apollo 16 FANs Petrology and Chemistry of Ancient Highlands Rocks in Soils Due to the importance of FANs in constraining the earliest crustal evolution of the Moon, it behooves us to find and analyze "new" samples made available either by soil and breccia pull-apart studies or through careful inspection of newly opened cores, such as 68001/2. The results of these studies have led us to request several more "white" fragments from this core Later Plutonic Rocks in the Lunar Crust Ion Probe Analyses of Minerals in Alkali Suite and Mg-suite Rocks We have used the ion probe at Washington University to determine trace-elements in individual minerals in non-FAN highlands rocks. These rocks are likely derived from differentiated plutons that were intruded into the nascent, FAN-rich, lunar crust after LMO crystallization. Our modelling of these results have led us to suggest that parental magmas for the highlands Mg-suite and the Alkali Suite (i.e., non-FAN crustal rocks) were derived from primitive KREEP basalts. These basalts were melts of the deep lunar interior that assimilated urKREEP, trapped in upper mantle cumulates, during ascent to the surface, and may also have assimilated anorthositic crust Highlands Rock Fragments in Lunar Soils Our understanding of the igneous history of highlands material adjacent to the Apollo 12 landing site is based on only 8 "probably pristine" clasts and fragments from soils and breccias in the Apollo collections. In an attempt to understand the distribution, character, and provenance of ostensible highlands material in the Procellarum basin, we picked through 2-10 mm fragments in soil 12001. We delineated 9 texturally pristine, coarse-grained samples and have studied their petrographic relationships and mineral chemistry. We are currently in the process of analyzing trace-elements in these rocks (including Ir, Re, and Au for ascertaining chemical pristinity) by ICP-MS at the Univ. of Notre Dame Impact processes on the Moon : Crystal-bearing lunar spherules Some lunar breccias, soils, and impact-melt rocks contain crystal-bearing lunar spherules (CLS). CLS are unlike the more common lunar impact glass spherules in that they are partly crystalline. Our studies suggest that these objects formed by impact-melting of at least 3 distinct, highland source regions on the Moon. Evidence provided by the CLS suggest that at least some meteoritic chondrules could have formed by impact-melting, although the rarity of CLS and ubiquity of chondrules suggests that impact processes on the Moon and asteroids differed in important ways.     Crystal-bearing lunar spherules (CLS) can be subdivided into feldspathic (a,b) and olivine-rich (c,d) varieties. The former appear to have been derived by impact- melting of typical lunar highland lithologies (FANs and Mg-suite rocks), whereas the provenance of the latter are unclear. Olivine-rich CLS, in particular, resemble meteoritic chondrules in mineralogy and texture, although their FeO/MnO abundance ratios suggest that they are of lunar origin. Lunar Resources We will be returning to the Moon within the near future, and it is imperative that we prepare now for establishment of a Lunar Base. Because it costs about $25,000 per pound to transport supplies to the Moon, it will be necessary to learn to "live off the land", much like our forefathers. It is the rocks and minerals and soils on the Moon that will be the basic raw materials for the settling and evolution of an autonomous manned lunar base. The unconsolidated nature of the lunar regolith makes it relatively easy to move, mine, and otherwise manipulate. Indeed, this regolith is presently the potential economic basis for a permanent manned presence at a Lunar Base. But, for an orderly preparation in anticipation of this return, extensive engineering/science studies are necessary. Considerable efforts are being expended on studies of the in-situ resource utilization (ISRU) of lunar materials. In reality, almost all that we know about the resource potentials of lunar materials has resulted from the scientific investigations of lunar samples performed during the last30 years. We are actively studying methods to beneficiate lunar soils for important minerals. One of these minerals is ilmenite, common in the maria; this could be the feedstock for one of the processes to produce oxygen on the Moon -- hydrogen reduction of ilmenite to produce Fe + TiO2 + O2 is one of the best choices at present. We have perfected methods to use X-ray digital imaging with an electron microprobe for fully quantiative modal analyses of the various minerals and glasses in lunar rocks and soils. This method is valuable in evaluating the resource potential of the soils, the first of the materials which will be utilized upon a return to the Moon Space Weathering and Remote Sensing of Planetary Regoliths. Space Weathering involves those effects that any object undergoes as a result of its exposure to the rigors of space. In the deep vacuum of space, the bombardment of micro-meteorites is sufficient to effectively "sand blast" surfaces, thereby affecting their albedo (reflecting ability). Solar-wind and cosmic particles significantly alter materials as well. In the case of "airless" bodies, such as our Moon, other planetary moons, and most asteroids, it the combined effects of space weathering [impact melting by micro-meteorites, particle implantation, spallation] that produce the regolith and soils on these bodies. This soil formation is entirely different from that on bodies with atmospheres, many of which also contain volatiles such as water (for example, the Earth). It is not the rocks, including the bedrock, of a body that we observe with various forms of remote sensing, but the thin venier of soil that covers most heavenly objects. Therefore, it is imperative that we completely understand the chemical and physical nature of this soil. Reflectance spectroscopy has proven to be an extremely useful tool for the remote compositional analysis of planetary surfaces and has provided major mineralogical and chemical constraints with which to better understand the geochemical and petrologic nature of planets, the Moon, asteroids, and other bodies of the Solar System. We are specifically addressing several problems associated with the interpretation of spectral reflectance data from airless bodies, using the Moon as our subject. The lunar soil collected by the six Apollo Missions to the Moon provides the "ground truth" for unraveling the effects of "space weathering," which mask and otherwise complicate the quantification of mineralogical and compositional data. We are employing x-ray digital imaging of grain mounts of lunar soils, using our Cameca SX-50 electron microprobe and various software. Deciphering the contributions made by the modes and compositions of the numerous soil components should permit evaluation of the observed spectra from the same soils. Dr. Carle Pieters, of Brown University, is measuring the spectral reflectance on each soil fraction studied here at UTK and will incorporate the results of our digital imaging into a model which will significantly increase the accuracy and precision of the compositional capabilities of reflectance spectroscopy, thereby furthering effective exploration of the Solar System Return to the Top of the Page. Return to the Current Research Projects Return to PGI Homepage