Solar wind contribution to surficial lunar water: Laboratory investigations

Remote infrared spectroscopic measurements have recently re-opened the possibility that water is present on the surface of the Moon. Analyses of infrared absorption spectra obtained by three independent space instruments have identified water and hydroxyl (-OH) absorption bands at ∼3 μm within the lunar surface. These reports are surprising since there are many mechanisms that can remove water but no clear mechanism for replenishment. One hypothesis, based on the spatial distribution of the -OH signal, is that water is formed by the interaction of the solar wind with silicates and other oxides in the lunar basalt. To test this hypothesis, we have performed a series of laboratory simulations that examine the effect of proton irradiation on two minerals: anorthite and ilmenite. Bi-directional infrared reflection absorption spectra do not show any discernable enhancement of infrared absorption in the 3 μm spectral region following 1 or 100 keV proton irradiation at fluences between 10¹⁶ and 10¹⁸ ions cm⁻². In fact, the post-irradiation spectra are characterized by a decrease in the residual O-H band within both minerals. Similarly, secondary ion mass spectrometry shows a decrease rather than an increase of the water group ions following proton bombardment of ilmenite. The absence of significant formation of either -OH or H₂O is ascribed to the preferential depletion of oxygen by sputtering during proton irradiation, which is confirmed by post-irradiation surface analysis using X-ray photoelectron spectroscopy measurements. Our results provide no evidence to support the formation of H₂O in the lunar regolith via implantation of solar wind protons as a mechanism responsible for the significant O-H absorption in recent spacecraft data. We determine an upper limit for the production of surficial -OH on the lunar surface by solar wind irradiation to be 0.5% (absorption depth).     

Nitrogen-bearing,aqueous fluid inclusions in some eclogites from the Western Gneiss Region of the Norwegian Caledonides

Minerals in eclogites from different localities in the Western Gneiss Region of the Norwegian Caledonides (age 425 Ma) contain a variety of fluid inclusions. The earliest inclusions recognized are contained in undeformed quartz grains, protected by garnet, and consist of H₂O+N₂ (with ). The reconstructed P-V-T-X properties of these fluid inclusions are compatible with peak or early-retrograde metamorphic conditions. Matrix minerals (quartz, garnet, apatite, plagioclase) contain a complex pattern of mostly truly secondary inclusions, dominated by CO₂ and N₂. The textural patterns and P-V-T-X properties of these inclusions are incompatible with the high pressures of the eclogite-forming metamorphic event, but suggest that they were formed during uplift, by a combination of remobilization of preexisting inclusions and influx of external fluids. The fluid introduced at a late stage was dominated by CO₂, and did not contain N₂. The present data agree with theoretical predictions of eclogite fluids from mineral equilibria, and highlight the differences between granulite (CO₂) and eclogite (H₂O+N₂) fluid regimes. The provenance of the nitrogen in the eclogite fluid inclusions represents an important, but unsolved question in the petrology of high-pressure metamorphic rocks.Contribution no. 68 to the Norwegian programme of the International Lithosphere Project     

A signal-to-noise model for ELF propagation in subsurface regions

Measurements of the natural extremely low-frequency (ELF) radio noise (known as Schumann resonances) in the period 1988-1989 have enabled average atmospheric noise levels and Schumann resonance parameters to be deduced. At 45 Hz, the average measured electric field was 41.6 dB·μV/m·√(Hz). It is assumed that the Schumann resonance noise field in the air-space in the vicinity of the observation point can be considered to be represented as the sum of four components, one arising from propagation over a short great-circle path, and a second representing a long great-circle path contribution, each of these having an upgoing and a downgoing part. The noise fields can then be estimated at any given depth below the ground (or sea) surface from the measured values in the air. The authors present results showing the computed fields produced in the sea from submerged horizontal electric quadrupole and vertical electric dipole man-made sources, and compare these with the subsurface atmospheric noise fields deduced from the experimental measurements     

UBV photometry of the Ap variable UZ Psc = HD 10783

NewUBV photometry, obtained between late 1965 and early 1969, is presented and combined with existing published photometry to derive an improved ephemeris for times of maximum brightness: 2439758.00+4 _d ^. .1328n. On leave from Dyer Observatory, Vanderbilt University, Nashville, Tennessee, U.S.A.     

Large-Area Back-Illuminated CCD Imager Development

We describe recent work in the area of large, back-illuminated CCD imagers at M.I.T. Lincoln Laboratory as well as new technology applicable to astronomy. We completed in 1995 the development of a 2560 x 1960-pixel frame-transfer imager that filled a 100-mm wafer and several back-illuminated versions of this device were completed. More recently we have begun the development, in collaboration with the U. of Hawaii, of a three-side abuttable 2k x 4k CCD for a multi-chip focal plane. In the unused chord area of the wafer layout, we added test imagers as development vehicles for blooming control and for the demonstration of a CCD that is capable of charge transfer in all four directions. We expect the latter to find application as an electronic means of performing tip-tilt correction to compensate for atmospheric turbulence.     

Observations concerning the relationship between the quiet-time ring current and electron temperatures at trough latitudes

The relationship between the simultaneously observed positions of the maximum omnidirectional flux of the quiet-time ring current positive ions (Λ_φ) and the maximum electron temperature Λ_T in the trough is studied in the midnight sector of the topside ionosphere. Λ_φ maps to the inner edge of the plasma sheet where ring current fluxes change from nearly isotropic to trapped. At altitudes near 2500 km, the electron temperature at trough latitudes were always sharply peaked. Although Λ_φ varied with the level of geomagnetic activity, (Λ_φ ? Λ_T) did not. These observations support the hypothesis that the quiet-time ring current is the source of elevated electron temperatures found near the plasmapause. Below 1300 km, peaked electron temperature distributions in the trough were not consistent features of the data. It is shown that (Λ_φ ? Λ_T) increased with decreasing altitude. The possible influences of a westward component to the convective electric field and ionospheric refraction of ion cyclotron waves are discussed.     

Development of management measures for the groundfish fishery in Atlantic Canada : A case study of the Nova Scotia inshore fleet

Subsequent to extension of fishery jurisdiction in 1977 it was Canadian policy to favour the inshore sector in rehabilitation of the Canadian groundfish fishery. Catch allocation, limited entry licensing and vessel replacement policies were implemented, which at first allowed and then increasingly attempted to limit inshore fleet expansion, which was being encouraged through financial assistance programmes. New regulatory authorities wer obtained to deal with the increasingly difficult task of limiting annual harvests to catch quota levels. A 1986 study concluded that the licensed capacity of the Nova Scotia inshore fleet was approximately four times that required to exploit the resource at target levels. As a result of a government task force report released in January 1990, substantial changes were made in the control of fishing by inshore fleets, including establishment of an individual boat catch quota system for some sectors. This article documents the regulatory actions taken to date to control inshore fleet development and annual fishing activities, and the responses of fishermen to these, as a possible guide to the implementation of new approaches.     

Alkoxyquinoline O-dealkylation: A new fluorimetric assay for hydrocarbon-induced cytochrome P450 in fish

The O-dealkylation of a new series of substrates, the alkoxyquinolines, provides a new easy fluorimetric assay for measuring the induction of cytochrome P450 by polycyclic aromatic hydrocarbons and drilling mud oil in fish. Expression of the results as a ratio between the inducible butyloxyquinoline O-dealkylation (BuQOD) activity and the non-inducible benzyloxyquinoline O-dealkylation (BeQOD) activity (i.e. the ‘BuQOD:-BeQOD quotient’) maximises the degree of induction measured and minimises the degree of inter-animal variation.     

Late Pleistocene glaciers in Darhad Basin, northern Mongolia

Late Pleistocene glaciers around Darhad Basin advanced to near their maximum positions at least three times, twice during the Zyrianka glaciation (at ∼ 17-19 ka and ∼ 35-53 ka), and at least once earlier. The Zyrianka glaciers were smaller than their predecessors, but the equilibrium-line altitude (ELA) difference was < 75 m. End moraines of the Zyrianka glaciers were ∼ 1600 m asl; ELAs were 2100-2400 m asl. ¹⁴C and luminescence dating of lake sediments confirm the existence of paleolake highstands in Darhad Basin before ∼ 35 ka. Geologic evidence and ¹⁰Be cosmic-ray exposure dating of drift suggests that at ∼ 17-19 ka the basin was filled at least briefly by a glacier-dammed lake ∼ 140 m deep. However, lake sediments from that time have not yet been recognized in the region. A shallower paleolake briefly occupied the basin at ∼ 11 ka, but between ∼ 11 and 17 ka and after ∼ 10 ka the basin was probably largely dry. The timing of maximum glacier advances in Darhad appears to be approximately synchronous across northern Mongolia, but different from Siberia and western Central Asia, supporting the inference that paleoclimate in Central Asia differed among regions.     

Woodcutters goldfield: Gold in an Archaean granite,Kalgoorlie, Western Australia

The 43 t (1.4 Moz) of gold in the Woodcutters goldfield 50 km north of Kalgoorlie has wide geological significance in terms of gold in Archaean granite, as well as its local commercial and exploration significance. Woodcutters is already one of the largest Archaean gold systems in granite, and is unusual in being so far laterally from the nearest greenstone belt. Gold in the Federal zone, one of the deposits making up the Woodcutters goldfield, is hosted in hornblende‐biotite granodiorite,6 km from the mapped contact with greenstone. In Federal open pit, the granodiorite is coarse‐grained in the northern half, and a fine‐grained granodiorite in the south, with both hosting gold. These two types of granodiorite are rather similar in both mineralogy and geochemistry. There is also a subordinate fine‐grained monzodiorite. The Federal gold mineralisation is in a northwest‐striking, northeast‐dipping (315° strike/60°E dip) shear zone in the Scotia granite. Variation in grainsize of the host rocks might have affected the style of deformation with more brittle fabrics in the coarse‐grained phase and more ductile fabrics prominent in the fine‐grained granodiorite. Hydrothermal alteration is extensively developed around the Federal deposit and is a useful vector towards gold mineralisation. Distal epidote alteration surrounds a proximal muscovite‐biotite alteration zone that contains quartz‐sulfide veins. The alteration shares some of the common alteration characteristics of Archaean greenstone‐hosted gold, but differs in that carbonate‐chlorite alteration is only weakly developed. This difference is readily explained in terms of host‐rock composition and lower concentrations of Fe, Mg and Ca in the granite compared with greenstone. Fluid‐inclusion studies demonstrate that the fluids associated with the hydrothermal alteration at Woodcutters shared the common characteristics of fluids in Archaean greenstone gold, namely low‐salinity and dominant H₂O–CO₂. Fluid inclusions with moderate salinity were found in one fresh sample away from mineralisation, and are inferred to represent possible magmatic fluid. There is no evidence of a granite‐derived fluid being responsible for gold mineralisation. The granodiorite host rock had cooled, crystallised and had at least started to undergo deformation prior to gold introduction. The distribution of gold mineralisation in the Woodcutters goldfield has the style, shape and orientation comparable with greenstone‐hosted gold deposits in the same region. The northwest trend, the quartz veining and simple pyrite mineralogy are all features common to other greenstone‐hosted gold deposits near Kalgoorlie such as Mt Pleasant. The alteration fluid appears to have penetrated the granite on the scale of many hundreds of metres, causing large‐scale alteration. Woodcutters gold mineralisation resulted from the same metamorphic fluid processes that led to formation of greenstone gold deposits. In this metamorphic model, granitic rocks are predicted to be less‐favourable gold hosts than mafic rocks for two reasons. Granitic rocks do not generally fracture during regional deformation in such a way as to create large‐scale dilation. Furthermore, with less iron and no carbon, granitic rocks have lower potential to precipitate gold from solution by wall‐rock reaction. The metamorphic model predicts that those granite types with higher Fe should host better gold deposits, all other factors being equal. Accordingly, tonalite‐trondhjemite and hornblende‐bearing granodiorite should provide better environments for major gold deposits compared with monzogranite, and granite sensu stricto, as borne out by Woodcutters, but mafic rocks should be better hosts than any of these felsic to intermediate rocks.