Breccias from the lunar highlands: preliminary petrographic report on apollo 16 samples 60017 and 63335

Lunar samples 60017,4 and 63335,14 are composed of microbreccias and devitrified glass. These components are predominantly anorthositic, with the exception of a cryptocrystalline clast found in the microbreccia portion of 63335,14 which contains 2.7 percent potassium oxide and 66.7 percent silicon dioxide. The samples have been subjected to extreme shock and thermal metamorphism. The parent materials of the microbreccias include both a coarse-grained anorthosite and a fine-grained subophitic anorthositic gabbro.     

Mineralogy and petrology of coarse particulate material from lunar surface at tranquillity base

Five grams of coarse fines (10085,11) contains 1227 grains, mostly mafic holocrystalline rock fragments, microbreccia, and glass spatter and agglomerates with less abundant anorthosite fragments and regularly shaped glass. The crystalline lithic fragments in the coarse fines and microbreccias represent a closely related suite of gabbroid igneous rocks that have a wider range of modal analyses and textures than seen in the larger crystalline rock samples returned by Apollo 11. Petrographic evidence of shock metamorphism is common, and the abundant glass is almost all shock-produced. None of the glass observed is similar to tektite glass.     

Three-dimensional structure of Hayabusa samples: origin and evolution of Itokawa regolith

Regolith particles on the asteroid Itokawa were recovered by the Hayabusa mission. Their three-dimensional (3D) structure and other properties, revealed by x-ray microtomography, provide information on regolith formation. Modal abundances of minerals, bulk density (3.4 grams per cubic centimeter), and the 3D textures indicate that the particles represent a mixture of equilibrated and less-equilibrated LL chondrite materials. Evidence for melting was not seen on any of the particles. Some particles have rounded edges. Overall, the particles' size and shape are different from those seen in particles from the lunar regolith. These features suggest that meteoroid impacts on the asteroid surface primarily form much of the regolith particle, and that seismic-induced grain motion in the smooth terrain abrades them over time.     

Deformation of silicates from the sea of tranquillity

Plagioclase and olivine crystals in the crystalline rocks from the Sea of Tranquillity show little or no evidence of either static or dynamic deformation. The large disorientations in many of the pyroxene crystals are commonly consistent with slip on the system T -(100), t = [001], but these distortions are not due to plastic flow. They are ascribed to rapid growth and quenching phenomena as deduced from studies of chondrules and of quenched natural and experimentally produced melts. Some of the silicates in the breccias and regolith show evidence of shock deformation, from mild to intense, as indicated by pervasive featuring, shock lamallae, and partial transformatiion of pyroxene and plagioclase crystals to glass.     

Mineralogy and petrology of some lunar samples

Chemical analyses and norms of four samples are presented which confirm original estimates of low silica, unusual abundance of titania, and low oxidation state of the rocks. Accounts are given of mineralogy and petrology of fine-and coarse-grained igneous rocks and microbreccias with emphasis on chemical composition of individual minerals and glasses. The glasses are either spheres that scatter widely around the composition of lunar basalts or coating glasses that approximate basalts and microbreccias in composition.     

Gas-rich meteorites: possible evidence for origin on a regolith

The asymmetry of irradiation features of grains in the Kapoeta and Fayetteville meteorites suggests irradiation on a regolith before meteorite formation. Chondrules and broken grains require approximately 10(4) years of irradiation time between formation or fracturing and compaction into the meteorite. Shock erasure of tracks from irradiated Kapoeta feldspars requires a severe shock event during or after meteorite formation.     

Mineralogy, petrology, and surface features of lunar samples 10062,35, 10067,9, 10069,30, and 10085,16

The primary rocks are a sequence of titanium-rich basic volcanics, composed of clinopyroxene, plagioclase, and ilmenite with minor olivine, troilite, and native iron. The soil and microbreccias are respectively loose and compacted mixtures of fragments and aggregates of similar rocks, minerals, and glassy fragments and spheres. Impact events are reflected by the presence of shock metamorphosed rock fragments, breccias, and glasses and their resulting compaction to form complex breccias, glass-spattered surfaces, and numerous glass-lined craters. Chemistry of the glasses formed by the impact events is highly variable, and the high iron and nickel content of a few moundlike features suggests that at least some of the projectiles are iron and nickel-rich meteorites.     

The apollo 16 lunar samples: petrographic and chemical description

The preliminary characterization of the rocks and soils returned from the Apollo 16 site has substantiated the inference that the lunar terra are commonly underlain by plagioclase-rich or anorthositic rocks. No evidence has been found for volcanic rocks underlying the regolith in the Apollo 16 region. In their place, we have found anorthositic rocks that are thoroughly modified by crushing and partial melting. The textural and chemical variations in these rocks provide some evidence for the existence of anorthositic complexes that have differentiated on a scale of tens to hundreds of meters. The occurrence of deep-seated or plutonic rocks in place of volcanic or pyroclastic materials at this site suggests that the inference from physiographic evidence that the latter materials are widespread in terra regions may be incorrect. Several additional, more specific conclusions derived from this preliminary examination are: 1) The combination of data from the Descartes region with data from the orbital x-ray fluorescence experiment indicates that some backside, highland regions are underlain by materials that consist of more than 80 percent plagioclase. 2) The soil or upper regolith between North Ray and South Ray has not been completely homogenized since the time of formation of these craters. 3) The chemistry of the soil indicates that rocks rich in potassium, uranium, and thorium, similar to those that prevail at the Fra Mauro site, are relatively abundant (10 to 20 percent) in the Descartes region. 4) The K/U ratio of the lunar crust is similar to that of the KREEP basalts. 5) The carbon content of the premare lunar crust is even lower than that of the mare volcanic rocks.     

Direct detection of projectile relics from the end of the lunar basin-forming epoch

The lunar surface, a key proxy for the early Earth, contains relics of asteroids and comets that have pummeled terrestrial planetary surfaces. Surviving fragments of projectiles in the lunar regolith provide a direct measure of the types and thus the sources of exogenous material delivered to the Earth-Moon system. In ancient [>3.4 billion years ago (Ga)] regolith breccias from the Apollo 16 landing site, we located mineral and lithologic relics of magnesian chondrules from chondritic impactors. These ancient impactor fragments are not nearly as diverse as those found in younger (3.4 Ga to today) regolith breccias and soils from the Moon or that presently fall as meteorites to Earth. This suggests that primitive chondritic asteroids, originating from a similar source region, were common Earth-Moon-crossing impactors during the latter stages of the basin-forming epoch.     

Galileo encounter with 951 gaspra: first pictures of an asteroid

Galileo images of Gaspra reveal it to be an irregularly shaped object (19 by 12 by 11 kilometers) that appears to have been created by a catastrophic collisional disruption of a precursor parent body. The cratering age of the surface is about 200 million years. Subtle albedo and color variations appear to correlate with morphological features: Brighter materials are associated with craters especially along the crests of ridges, have a stronger 1-micrometer absorption, and may represent freshly excavated mafic materials; darker materials exhibiting a significantly weaker 1-micrometer absorption appear concentrated in interridge areas. One explanation of these patterns is that Gaspra is covered with a thin regolith and that some of this material has migrated downslope in some areas.     

Itokawa dust particles: a direct link between S-type asteroids and ordinary chondrites

The Hayabusa spacecraft successfully recovered dust particles from the surface of near-Earth asteroid 25143 Itokawa. Synchrotron-radiation x-ray diffraction and transmission and scanning electron microscope analyses indicate that the mineralogy and mineral chemistry of the Itokawa dust particles are identical to those of thermally metamorphosed LL chondrites, consistent with spectroscopic observations made from Earth and by the Hayabusa spacecraft. Our results directly demonstrate that ordinary chondrites, the most abundant meteorites found on Earth, come from S-type asteroids. Mineral chemistry indicates that the majority of regolith surface particles suffered long-term thermal annealing and subsequent impact shock, suggesting that Itokawa is an asteroid made of reassembled pieces of the interior portions of a once larger asteroid.     

Spectroscopic observations of Mercury's surface reflectance during MESSENGER's first Mercury flyby

During MESSENGER's first flyby of Mercury, the Mercury Atmospheric and Surface Composition Spectrometer made simultaneous mid-ultraviolet to near-infrared (wavelengths of 200 to 1300 nanometers) reflectance observations of the surface. An ultraviolet absorption (<280 nanometers) suggests that the ferrous oxide (Fe2+) content of silicates in average surface material is low (less than 2 to 3 weight percent). This result is supported by the lack of a detectable 1-micrometer Fe2+ absorption band in high-spatial-resolution spectra of mature surface materials as well as immature crater ejecta, which suggests that the ferrous iron content may be low both on the surface and at depth. Differences in absorption features and slope among the spectra are evidence for variations in composition and regolith maturation of Mercury's surface.     

The surface composition and temperature of asteroid 21 Lutetia as observed by Rosetta/VIRTIS

The Visible, InfraRed, and Thermal Imaging Spectrometer (VIRTIS) on Rosetta obtained hyperspectral images, spectral reflectance maps, and temperature maps of the asteroid 21 Lutetia. No absorption features, of either silicates or hydrated minerals, have been detected across the observed area in the spectral range from 0.4 to 3.5 micrometers. The surface temperature reaches a maximum value of 245 kelvin and correlates well with topographic features. The thermal inertia is in the range from 20 to 30 joules meter(-2) kelvin(-1) second(-0.5), comparable to a lunarlike powdery regolith. Spectral signatures of surface alteration, resulting from space weathering, seem to be missing. Lutetia is likely a remnant of the primordial planetesimal population, unaltered by differentiation processes and composed of chondritic materials of enstatitic or carbonaceous origin, dominated by iron-poor minerals that have not suffered aqueous alteration.     

Imaging of small-scale features on 433 Eros from NEAR: evidence for a complex regolith

On 25 October 2000, the Near Earth Asteroid Rendevous (NEAR)-Shoemaker spacecraft executed a low-altitude flyover of asteroid 433 Eros, making it possible to image the surface at a resolution of about 1 meter per pixel. The images reveal an evolved surface distinguished by an abundance of ejecta blocks, a dearth of small craters, and smooth material infilling some topographic lows. The subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter-sized blocks.     

Lunar regolith at tranquillity base

The regolith at Tranquillity Base is a layer of fragmental debris that ranges in thickness from about 3 to 6 meters. The thickness of the regolith and the exposure histories of its constituent fragments can be related, by means of a relatively simple model, to the observed crater distribution.     

Lonar lake, India: an impact crater in basalt

Discovery of shock-metamorphosed material establishes the impact origin of Lonar Crater. Coarse breccia with shatter coning and microbreccia with moderately shocked fragments containing maskelynite were found in drill holes through the crater floor. Trenches on the rim yield strongly shocked fragments in which plagioclase has melted and vesiculated, and bombs and spherules of homogeneous rock melt. As the only known terrestrial impact crater in basalt, Lonar Crater provides unique opportunities for comparison with lunar craters. In particular, microbreccias and glass spherules from Lonar Crater have close analogs among the Apollo specimens.     

Potassium-uranium systematics of apollo 11 and apollo 12 samples: implications for lunar material history

Apollo 11 and Apollo 12 lunar rock suites differ in their potassium-uranium abundance systematics. This difference indicates that relatively little exchange of regolith material has occurred between Mare Tranquillitatis and Oceanus Procellarum. The two suites appear to have been derived from materials of identical potassium and uranium content. It appears unlikely that bulk lunar material has the ratio of potassium to uranium found in chondrites. However, systematic differences in the potassium-uranium ratio between Apollo samples and crustal rocks of the earth do not preclude a common potassium-uranium ratio for bulk earth and lunar material.     

Discovery of vapor deposits in the lunar regolith

Lunar soils contain micrometer-sized mineral grains surrounded by thin amorphous rims. Similar features have been produced by exposure of pristine grains to a simulated solar wind, leading to the widespread belief that the amorphous rims result from radiation damage. Electron microscopy studies show, however, that the amorphous rims are compositionally distinct from their hosts and consist largely of vapor-deposited material generated by micrometeorite impacts into the lunar regolith. Vapor deposits slow the lunar erosion rate by solar wind sputtering, influence the optical properties of the lunar regolith, and may account for the presence of sodium and potassium in the lunar atmosphere.     

Opaque minerals of the lunar rocks and dust from mare tranquillitatis

The opaque minerals in the lunar rocks 10047, 10050, 10057, 10059, 10068 and in the dust were studied. Rock 10047 contains ilmenite as a main component besides Al-bearing chromian ulv?spinel, a new Ti, Fe, Zr, Y, Ca silicate, troilite, cobaltian alpha Fe, minor hafnian baddeleyite and dysanalyte. Dysanalyte contains Ca, Ti, and Fe as major elements and shows concentrations (rare earth elements together approximately 10 percent) of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Hf, Y, and Zr plus traces of Nb, Ba, and Na. The chemistry of ilmenite in the igneous rocks shows no appreciable variations. A new mineral of the solid solution series MgTi(2)O(5)-FeTi(2)O(5) has also been encountered in the polymict breccias. The microbreccias and the fines contain meteorite debris indicating an impact origin.     

3种FT基因诱导杨树早期开花比较

为了促进杨树早期开花,缩短杨树遗传育种周期,采用农杆菌AGL1介导的转化方法及热激诱导方法,进行了热激启动子HSP控制下的3类FT基因转化2种杨树无性系(353与717)诱导杨树早期开花的比较研究.结果表明:来自拟南芥的FT基因促花效果优于来自杨树的FT1和FT2基因;FT类基因与受体基因型/性别之间互作明显,开花较好...