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At least 73 records · Page 4Linked to original sources
USGS2006

Refined thorium abundances for lunar red spots: Implications for evolved, nonmare volcanism on the Moon

We have used improved knowledge of the spatial distribution of thorium (Th) on the lunar surface, in conjunction with a forward modeling analysis of Lunar Prospector gamma ray data, to estimate the thorium abundances of lunar red spots. The results from this study can be combined with preexisting compositional and morphologic evidence to suggest that Hansteen Alpha, the Gruithuisen domes, and the Lassell massif are silicic, nonmare, volcanic constructs, similar in nature to terrestrial rhyolite domes. We propose that either silicate liquid immiscibility or, more likely, basaltic underplating could have produced lunar rhyolite domes. Thus the Lunar Prospector data presented in this study provide new information about the full range of volcanic and crustal processes that could have occurred on the Moon.

Journal of Geophysical Research E: Planets↗
USGS2011

Lunar mare deposits associated with the Orientale impact basin: New insights into mineralogy, history, mode of emplacement, and relation to Orientale Basin evolution from Moon Mineralogy Mapper (M3) data from Chandrayaan-1

Moon Mineralogy Mapper (M3) image and spectral reflectance data are combined to analyze mare basalt units in and adjacent to the Orientale multiring impact basin. Models are assessed for the relationships between basin formation and mare basalt emplacement. Mare basalt emplacement on the western nearside limb began prior to the Orientale event as evidenced by the presence of cryptomaria. The earliest post-Orientale-event mare basalt emplacement occurred in the center of the basin (Mare Orientale) and postdated the formation of the Orientale Basin by about 60-100 Ma. Over the next several hundred million years, basalt patches were emplaced first along the base of the Outer Rook ring (Lacus Veris) and then along the base of the Cordillera ring (Lacus Autumni), with some overlap in ages. The latest basalt patches are as young as some of the youngest basalt deposits on the lunar nearside. M3 data show several previously undetected mare patches on the southwestern margins of the basin interior. Regardless, the previously documented increase in mare abundance from the southwest toward the northeast is still prominent. We attribute this to crustal and lithospheric trends moving from the farside to the nearside, with correspondingly shallower density and thermal barriers to basaltic magma ascent and eruption toward the nearside. The wide range of model ages for Orientale mare deposits (3.70-1.66 Ga) mirrors the range of nearside mare ages, indicating that the small amount of mare fill in Orientale is not due to early cessation of mare emplacement but rather to limited volumes of extrusion for each phase during the entire period of nearside mare basalt volcanism. This suggests that nearside and farside source regions may be similar but that other factors, such as thermal and crustal thickness barriers to magma ascent and eruption, may be determining the abundance of surface deposits on the limbs and farside. The sequence, timing, and elevation of mare basalt deposits suggest that regional basin-related stresses exerted control on their distribution. Our analysis clearly shows that Orientale serves as an excellent example of the early stages of the filling of impact basins with mare basalt. Copyright ?? 2011 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗
USGS2011

Optical maturity variation in lunar spectra as measured by Moon Mineralogy Mapper data

High spectral and spatial resolution data from the Moon Mineralogy Mapper (M3) instrument on Chandrayaan-1 are used to investigate in detail changes in the optical properties of lunar materials accompanying space weathering. Three spectral parameters were developed and used to quantify spectral effects commonly thought to be associated with increasing optical maturity: an increase in spectral slope ("reddening"), a decrease in albedo ("darkening"), and loss of spectral contrast (decrease in absorption band depth). Small regions of study were defined that sample the ejecta deposits of small fresh craters that contain relatively crystalline (immature) material that grade into local background (mature) soils. Selected craters are small enough that they can be assumed to be of constant composition and thus are useful for evaluating trends in optical maturity. Color composites were also used to identify the most immature material in a region and show that maturity trends can also be identified using regional soil trends. The high resolution M3 data are well suited to quantifying the spectral changes that accompany space weathering and are able to capture subtle spectral variations in maturity trends. However, the spectral changes that occur as a function of maturity were observed to be dependent on local composition. Given the complexity of space weathering processes, this was not unexpected but poses challenges for absolute measures of optical maturity across diverse lunar terrains. Copyright 2011 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗
USGS2011

The Mairan domes: silicic volcanic constructs on the Moon

The Mairan domes are four features located in northern Oceanus Procellarum at ∼312.3E, 41.4N on the Moon. High resolution visible imagery, visible-to-mid-IR spectra, and Lunar Prospector Th abundance data all indicate that these four domes have a composition that is consistent with derivation from a Si-rich, highly evolved magma.

Geophysical Research Letters↗
USGS2012

Galileo observations of Post-Imbrium lunar craters during the first Earth-Moon flyby

Copernican‐age craters are among the most conspicuous features seen on the far side and western limb of the Moon in the Galileo multispectral images acquired in December 1990. Among the new morphologic observations of far‐side craters are bright rays, continuous ejecta deposits, and dark rings associated with probable impact‐melt veneers. These observations suggest that the mapped age assignments of several large far‐side craters (Ohm, Robertson, and possibly Lowell and Lenz) need revision. New crater size‐frequency measurements on Lunar Orbiter images suggest the following age reassignments: Hausen (170 km diameter), Pythagoras (120 km), and Bullialdus (61 km) from Eratosthenian to Upper Imbrian, and Carpenter (60 km) and Harpalus (39 km) from Copernican to Eratosthenian. Colors and albedos of craters (away from impact‐melt veneers) are correlated with their geologic emplacement ages as determined from counts of superposed craters; these age‐color relations are used to estimate the emplacement age (time since impact event) for other Copernican‐age craters. These age‐color relations indicate a probable Copernican age for 27 far‐side or western limb craters larger than 10 km diameter that were not previously mapped as Copernican. The apparent deficiency of Copernican craters on the far side compared with the near side in published geologic maps is not present in our data. Age‐color trends differ between mare and highland regions and between the interiors and continuous ejecta of the craters. Similar trends are established for color and albedo versus soil‐maturity indices for the returned lunar samples, with distinct trends for mare and highland soils. However, the mare versus highland offsets are reversed in the two comparisons. These relations can be explained by variations in regolith thicknesses and rates of mixing with relatively fresh, crystalline ejecta. Therefore, the soil‐maturity trends represent longer geologic time periods in regions with thinner regoliths, such as the maria.

Journal of Geophysical Research E: Planets↗
USGS2009

Magma evolution and ascent at the craters of the moon and neighboring volcanic fields, southern Idaho, USA: Implications for the evolution of polygenetic and monogenetic volcanic fields

The evolution of polygenetic and monogenetic volcanic fields must reflect differences in magma processing during ascent. To assess their evolution we use thermobarometry and geochemistry to evaluate ascent paths for neighboring, nearly coeval volcanic fields in the Snake River Plain, in south-central Idaho, derived from (1) dominantly Holocene polygenetic evolved lavas from the Craters of the Moon lava field (COME) and (2) Quaternary non-evolved, olivine tholeiites (NEOT) from nearby monogenetic volcanic fields. These data show that NEOT have high magmatic temperatures (1205 + or - 27 degrees C) and a narrow temperature range (< 25 degrees C) at any given depth; NEOT parent magmas partially crystallize within the middle crust (14-17 km), but with little time for cooling or assimilation. In contrast, COME magmas partially crystallize at similar depths, but at any given depth exhibit lower temperatures (by ~40 degrees C), and wider temperature ranges (>50 degrees C). Prolonged storage of COME magmas allows them to evolve to higher 87 Sr/ 86 Sr and SiO 2 , and lower MgO and 143 Nd/ 144 Nd. Most importantly, ascent paths control evolution: NEOT often erupt near the axis of the plain where high-flux (Yellowstone-related), pre-Holocene magmatic activity replaces granitic middle crust with basaltic sills, resulting in a net increase in NEOT magma buoyancy. COME flows erupt off-axis, where felsic crustal lithologies sometimes remain intact, providing a barrier to ascent and a source for crustal contamination. A three-stage ascent process explains the entire range of erupted compositions. Stage 1 (40-20 km): picrites are transported to the middle crust, undergoing partial crystallization of olivine + or - clinopyroxene. COME magmas pass through unarmored conduits and assimilate 1% or less of ancient gabbroic crust having high Sr and 87 Sr/ 86 Sr and low SiO 2 . Stage 2 (20-10 km): magmas are stored within the middle crust, and evolve to moderate MgO (10%). NEOT magmas, reaching 10% MgO, are positively buoyant and migrate through the middle crust. COME magmas remain negatively buoyant and so crystallize further and assimilate middle crust. Stage 3 (15-0 km): final ascent and eruption occurs when volatile contents, increased by differentiation, are sufficient (1-2 wt % H 2 O) to provide magma buoyancy through the middle (and upper) crust.

Idaho↗
USGS2009

Size and shape of Saturn's moon Titan

Cassini observations show that Saturn’s moon Titan is slightly oblate. A fourth-order spherical harmonic expansion yields north polar, south polar, and mean equatorial radii of 2574.32 ± 0.05 kilometers (km), 2574.36 ± 0.03 km, and 2574.91 ± 0.11 km, respectively; its mean radius is 2574.73 ± 0.09 km. Titan’s shape approximates a hydrostatic, synchronously rotating triaxial ellipsoid but is best fit by such a body orbiting closer to Saturn than Titan presently does. Titan’s lack of high relief implies that most—but not all—of the surface features observed with the Cassini imaging subsystem and synthetic aperture radar are uncorrelated with topography and elevation. Titan’s depressed polar radii suggest that a constant geopotential hydrocarbon table could explain the confinement of the hydrocarbon lakes to high latitudes.

Science↗
USGS1963

Surface material of the moon

A skeletal fuzz that consists mostly of open space probably covers the moon to a depth of several millimeters or centimeters. The solid part of the fuzz probably consists of randomly oriented linear units, with or without enlarged nodes, which either anastomose in a mesh or are branching.

Science↗
USGS1994

Clementine observations of the Aristarchus region of the moon

Multispectral and topographic data acquired by the Clementine spacecraft provide information on the composition and geologic history of the Aristarchus region of the moon. Altimetry profiles show the Aristarchus plateau dipping about 1° to the north-northwest and rising about 2 kilometers above the surrounding lavas of Oceanus Procellarum to the south. Dark, reddish pyroclastic glass covers the plateau to average depths of 10 to 30 meters, as determined from the estimated excavation depths of 100- to 1000-meter-diameter craters that have exposed materials below the pyroclastics. These craters and the walls of sinuous rilles also show that mare basalts underlie the pyroclastics across much of the plateau. Near-infrared images of Aristarchus crater reveal olivine-rich materials and two kilometer-sized outcrops of anorthosite in the central peaks. The anorthosite could be either a derivative of local magnesium-suite magmatism or a remnant of the ferroan anorthosite crust that formed over the primordial magma ocean.

Science↗
USGS1996

Late Proterozoic and Paleozoic tides, retreat of the moon, and rotation of the earth

The tidal rhythmites in the Proterozoic Big Cottonwood Formation (Utah, United States), the Neoproterozoic Elatina Formation of the Flinders Range (southern Australia), and the Lower Pennsylvanian Pottsville Formation (Alabama, United States) and Mansfield Formation (Indiana, United States) indicate that the rate of retreat of the lunar orbit is d ξ/ dt ∼ k 2 sin(2δ) (where ξ is the Earth-moon radius vector, k 2 is the tidal Love number, and δ is the tidal lag angle) and that this rate has been approximately constant since the late Precambrian. When the contribution to tidal friction from the sun is taken into account, these data imply that the length of the terrestrial day 900 million years ago was ∼18 hours.

Alabama, Indiana, Utah↗
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↗
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↗
USGS1967

(LAC-93) Geologic map of the Mare Humorum region of the moon

The principal feature of the Mare Humorum region is the Humorum basin, a circular mare basin approximately 200 km (kilometer) in diameter . The basin formed early in the history of the moon and was later flooded by mare material. Impact cratering with attendant erosion and aggradation and episod ic volcanism and faulting have occurred in the region . The inferred history of the Humorum basin is similar to that of the Imbrium basin ( S hoemaker and Hackman, 1962; Titley , 1964), but the more subdued topography and the larger density of craters on the rim of the Humorum basin suggest that it is older than the Imbrium basin.

IMAP↗
USGS1967

(LAC-38) Geologic map of the Seleucus quadrangle of the moon

The Seleucus quadrangle lies in the northwestern part of the Oceanus Procellarum , a large mare of irregular shape in the western part of the earthside hemisphere of the Moon. Material of the mare occupies most of the quadrangle. Craters ranging from 1 to 44 km in diameter are scattered over the smooth mare surface; in addition, a few isolated hills and ridges rise above the mare. In the east-central part of the quadrangle, the Aristarchus plateau (informal name ) slopes gently westward and merges with the surrounding surface of Oceanus Procellarum . The plat eau is also known for its reddish color and light absorption properties (Wood, 1912), and areas where occasional reddish glows have been seen (Greenacre, 1965).

IMAP↗
USGS1968

(LAC-59) Geologic map of the Mare Vaporum quadrangle of the moon

The Mare Vaporum quadrangle is centrally l ocated on the near side of the Moon, southeast of the craterlike basin of Mare Imbrium . Stratigraphic units and structures peripheral to the basin and rela ted to it domina te the terra of the quadrangle, and one of the maria, S inus Medii , is in a trou g h that is concentric with the basin. The other principal maria, Mare Vaporum a n d Sinu s Aestuum , occupy craterlike basins that apparently antedate the Imbrium basin and developed independently of it. Some stratigraphic units and structures, mostly relatively young , are present that are not related to mare basin.

IMAP↗
USGS1969

(RLC-15) Geologic map of the Alphonsus GA region of the moon

This ma p is one of a series prepared from photographs transmitted by R anger IX (Jet Propulsion L ab ., 1966. , pls. A56-A58, B70-B82). It depicts the geology of some 724 sq km in the northeast p a rt of the floor of Alphon s us (diameter about 115 km), a typical flat-floored old terra crater or basin with subdued rim. Similar basins abound in the south-central tarrae of the visible hemisphere and on the far side of the Moon. Alphonsus is of particular inte re st, however, because of a well-developed interior rille system and a ssociated dark-halo craters.

IMAP↗
USGS1970

(ORB II-6 (100)) Geologic map of the Sabine D region of the moon, Lunar Orbiter site II P-6, southwestern Mare Tranquillitatis including Apollo landing site 2

This map sho w s the geology in and around Tranquillity Base where Apollo 11 landed, near the western end of early Apollo landing site 2 ( see index map ) , in the equatorial bel t of the Moon. The Sabine D region is in the southwestern part of the Mare T ranquillitatis . Most of the region lies within the Ju lius Caesar Quadrang l e (LAC 60) mapped at 1:1,000,000 by Mo r ris and Wilhelms (1967) .

IMAP↗
USGS1971

Geologic map of the Oppolzer A region of the Moon Lunar Orbiter Site II P-8, Sinus Medii including Apollo landing sites 3 and 3R

The map shows the regional geology of the Oppolzer A region of the moon, where potential Apollo landing site s 3 and 3R are located. Site 3R includes a prominent mare ridge and is of greater scientific interest (Trask, 1969). The Oppolzer A region is in Sinus Medii , near the center of the lunar earthside hemisphere; it is als o important because surve yor VI successfully landed near the proposed Apollo landing areas. Sinus Med ii is a relatively small, densely cratered mare surrounded by terra plains and sculptured terra ( Wilhelms , 1968). The geology of the region is dominated by a rela tively high density of individual craters and crater clusters. Most of the craters are less than 800 meters in diameter and appear to be of secondary and primary impact origin.

IMAP↗