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Research about Moon

Source-linked reports with geographic coverage including Moon.

At least 55 records · Page 3Linked to original sources
USGS2001

Mineralogy of the last lunar basalts: Results from Clementine

The last major phase of lunar volcanism produced extensive high-titanium mare deposits on the western nearside which remain unsampled by landing missions. The visible and near-infrared reflectance properties of these basalts are examined using Clementine multispectral images to better constrain their mineralogy. A much stronger 1 μm ferrous absorption was observed for the western high-titanium basalts than within earlier maria, suggesting that these last major mare eruptions also may have been the most iron-rich. These western basalts also have a distinctly long-wavelength, 1 μm ferrous absorption which was found to be similar for both surface soils and materials excavated from depth, supporting the interpretation of abundant olivine within these deposits. Spectral variation along flows within the Imbrium basin also suggests variations in ilmenite content along previously mapped lava flows as well as increasing olivine content within subsequent eruptions.

Journal of Geophysical Research E: Planets↗
USGS2001

Lunar orbiter digitization and cartographic processing

Digitization and cartographic processing of 5 Lunar Orbiter (LO) IV frames (109H, 110H, 114H, 115H, and 114M) are now complete, and these data are available online at http://wwwflag.wr.usgs.gov/USGSFlag/Space/LunarOrbiter/lunorbWebtop.html. Coverage ofthese data extends from Eratosthenes crater on the west to Mare Serenitatis in the east, and from Aristoteles crater in the north to Rima Hyginus in the south. Geologic features in this area encompass a wide variety of lunar units, processes, and ages, and they include parts of the Apennine Mountains, the KREEP-rich Apennine Bench Formation, Rima Bode pyroclastics (Figure 1), Mare Vaporum, Sulpicius Gallus, and the Imbrium basin ejecta southeast of the basin rim. These data products demonstrate our capability for digitizing and cartographically processing the LO data.

Conference Paper↗
USGS1995

Further evidence for a low U/Pb source in the moon: U-Th-Pb, Sm-Nd, and Ar-Ar, isotopic systematics of lunar meteorite Yamato-793169

The coarse-grained lunar meteorites, Yamato-793169 and Asuka-881757, represent a new type of low-Ti mare basalt. This paper reports the results of a U-Th-Pb, Sm-Nd, and Ar-Ar isotopic study of Yamato-793169 performed as part of a consortium studies of lunar basaltic meteorites. The isotopic study was carried out on a small sample (100 mg) so that only three density fractions could be separated. These fractions were leached with dilute acid in order to eliminate terrestrial Pb contamination. However, the leaching procedure did not completely remove this contamination in some fractions and also apparently caused a fractionation of elements (U, Th, Pb) due to preferential leaching effects, producing a secondary disturbance of the systematics. Furthermore, the Ar-Ar analyses indicate that the isotopic systematics in this meteorite might have been disturbed sometime later than 750 Ma. For these reasons, the ages obtained using different isotopic systems disagree with each other and a precise formation age could not be obtained for this meteorite. However, using what results there are, two reasonable interpretations can be made: (1) the Sm-Nd system yielded an age of 3.4 Ga that could be interpreted as the formation age, assuming that this system is possibly the least disturbed during the metamorphic event(s) that this meteorite experienced at least once, and that all other isotopic systems and their corresponding ages were disturbed, and (2) the U-Pb system yielded a nearly concordant age of 3.8 Ga that could be interpreted as the formation age and the Sm-Nd isotopic systematics were somehow disturbed. We prefer the second interpretation for the reasons discussed below. On a concordia diagram, the CDT (Cañon Diablo troilite)-corrected U-Pb isotopic data yield a discordia line similar to the lunar catastrophic array, indicating that the source of the meteorite formed during early lunar differentiation (∼4.4 Ga) and that the basalt was generated near 3.9 Ga. Total Ar-Ar age on plagioclase is 3.26 Ga, which seems to be too old if the formation age is 3.4 Ga, because low temperature fractions lost large amounts of radiogenic 40 Ar during the late thermal event. If we assume a formation age of 3.8 Ga, the estimated source 238 U/ 204 Pb (μ) is 21.6 ± 3.5 and ϵ Nd is 3.9 ± 0.3. These results indicate that the source of Yamato-793169 is more depleted than Apollo 12 and 15 LT basalts, but less depleted than Asuka-881757. Therefore, Yamato-793169 may represent a new type of LT- or VLT-like mare basalt that is different from Asuka-881757. The wide variety of lead and neodymium isotopic characteristics among LT and VLT mare basalts indicate that the lunar mantle was very heterogeneous with respect to trace element abundances.

Geochimica et Cosmochimica Acta↗
USGS1994

The Clementine mission to the Moon: Scientific overview

In the course of 71 days in lunar orbit, from 19 February to 3 May 1994, the Clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths. These data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side. In addition, laser-ranging measurements provided the first view of the global topographic figure of the moon. The topography of many ancient impact basins has been measured, and a global map of the thickness of the lunar crust has been derived from the topography and gravity.

Science↗
USGS1987

The geologic history of the Moon

More than two decades of study have established the major features of lunar geologic style and history. The most numerous and significant landforms belong to a size-morphology series of simple craters, complex craters, and ringed basins that were formed by impacts. Each crater and basin is the source of primary ejecta and secondary craters that, collectively, cover the entire terra. The largest impacts thinned, weakened, and redistributed feldspathic terracrustal material averaging about 75 km in thickness. Relatively small volumes of basalt, generated by partial remelting of mantle material, were erupted through the thin subbasin and subcrater crust to form the maria that cover 16 percent of the lunar surface. Tectonism has modified the various stratigraphic deposits relatively little; most structures are confined to basins and large craters. This general geologic style, basically simple though complex in detail, has persisted longer than 4 aeons (1 aeon = 10 9 yr). Impacts began to leave a visible record about 4.2 aeons ago, after the crust and mantle had differentiated and the crust had solidified. At least 30 basins and 100 times that many craters larger than 30 km in diameter were formed before a massive impact created the Nectaris basin about 3.92 aeons ago. Impacts continued during the ensuing Nectarian Period at a lesser rate, whereas volcanism left more traces than during pre-Nectarian time. The latest basin-forming impacts created the giant and still-conspicuous Imbrium and Orientale basins during the Early Imbrian Epoch, between 3.85 and 3.80 aeons ago. The rate of crater-forming impacts continued to decline during the Imbrian Period. Beginning in the Late Imbrian Epoch, mare-basalt flows remained exposed because they were no longer obscured by many large impacts. The Eratosthenian Period (3.2-1.1 aeons ago) and the Copernican Period (1.1 aeons ago to present) were times of lesser volcanism and a still lower, probably constant impact rate. Copernican impacts created craters whose surfaces have remained brighter and topographically crisper than those of the more ancient lunar features.

Professional Paper↗
USGS1985

Remote sensing of lunar pyroclastic mantling deposits

Mantling deposits on the Moon are considered to be pyroclastic units emplaced on the lunar surface as a result of explosive fire fountaining. These pyroclastic units are characterized as having low albedos, having smooth fine-textured surfaces, and consisting in part of homogeneous, Febearing volcanic glass and partially crystallized spheres. Mantling units exhibit low returns on depolarized 3.8-cm radar maps, indicating an absence of surface scatterers in the 1- to 50-cm-size range. A number of reflectance spectra from several regional pyroclastic deposits are presented for the first time; these data support a previous interpretation that mantling units have a unique spectral signature which is indicative of the presence of a significant Fe-bearing volcanic glass component. The Rima Bode region is discussed as an example of an area in which several types of remote sensing data (including 3.8-cm radar, spectral reflectance, and multispectral vidicon data) were used to reconstruct the geologic events surrounding the emplacement of a regional pyroclastic mantling deposit. The recognition of numerous varieties of volcanic glass samples, especially relatively high-albedo (e.g., green, yellow) glasses, suggests the existence of additional, unrecognized mantling deposits with albedos higher than those studied to date. On the basis of the remote sensing data summarized and presented, five new areas have been identified which may represent higher-albedo regional pyroclastic deposits.

Icarus↗
USGS1979

The Moon: Sources of the crustal magnetic anomalies

Previously unmapped Apollo 16 subsatellite magnetometer data collected at low altitudes over the lunar near side are presented. Medium-amplitude magnetic anomalies exist over the Fra Mauro and Cayley Formations (primary and secondary basin ejecta emplaced 3.8 to 4.0 billion years ago) but are nearly absent over the maria and over the craters Copernicus, Kepler, and Reiner and their encircling ejecta mantles. The largest observed anomaly (radial component ∼21 gammas at an altitude of 20 kilometers) is exactly correlated with a conspicuous light-colored deposit on western Oceanus Procellarum known as Reiner γ. Assuming that the Reiner γ deposit is the source body and estimating its maximum average thickness as 10 meters, a minimum mean magnetization level of 5.2 ± 2.4 × 10 –2 electromagnetic units per gram, or ∼500 times the stable magnetization component of the most magnetic returned sample, is calculated. An age for its emplacement of ≲ 2.9 billion years is inferred from photogeologic evidence, implying that magnetization of lunar crustal materials must have continued for a period exceeding 1 billion years.

Science↗
USGS1979

Geologic map of the south side of the Moon

The map of the lunar region below lat 45 ˚ S. is the sixth part of a complete geolog ic recon naissance mapping of the moon at 1:5,000,000 scale. The upper half of the map portrays the geology of the earth-facing or near side, and the lower half shows terrain that was unknown before spacecr aft photography. The near side that was well photographed at resolutions of 0.1 to 0.5 km by Lunar Orbiter IV, but coverage of the far side is uneven quality (fig. 1). The geology of a small area near the south pole that was in shadow during the Orbiter missions can be partly inferred from the nature of adjacent units.

IMAP↗
USGS1978

The moon in Heiligenschein

An analysis of 25 photometric digital images of the moon has been carried out to obtain a single image in a new mapping parameter, the Heiligenschein exponent. The data necessarily represent a range of lunar phases, but all are within 10 hours of full moon. The new parameter characterizes the rate at which lunar features brighten as their local phase angles approach zero. Although considerable contrast is present in this parameter, there is only a small correlation with normal albedo. In particular, the large albedo difference between maria and highlands is not simply reflected in Heiligenschein differences, which are larger within each category of terrain than the difference between the Heiligenschein averages of each. A correlation with age may be present in both the maria and the highlands, but its determination will require separation into distinct geochemical provinces.

Science↗
USGS1978

Geologic map of the central far side of the Moon

This map is one of a series of geologic maps t hat will cover the entire Moon at a scale of 1:5,000,000. The geology of the central far side is compiled largely from NASA Lunar Orbiter and Apollo photographs and Soviet Zond photographs; the discussion and interpretation of geologic units incorporate the geochemical and geophysical data obtained from orbiting s p acecraft. Geologic units are based on the stratigraphic framework established by Shoemaker and Hackman (1962) as subsequently revised (summarized by McCauly , 19 67 ; Wilhelms , 1970; Mutch , 1972; Stuart-Alexander and Wilhelms , 1975). Description of map units is brief because they largely follow units described on the nearside 1:5,000,000 map of Wilhelms and McCauley (1971). The reader unfamiliar with lunar maps, mapping principles, and terminology is referred to that map. Only new units and features or units whose origins are still much in doubt are discussed here.

IMAP↗