Possible magnetic effects due to fine particle metal and intergrown phases in lunar samples

Electron microscopy has confirmed the existence of both body centered cubic (BBC)-α metal and face centered cubic (FCC)-γ metal in lunar fines and breccia samples. Under appropriate conditions of composition, size, and other constraints iron-nickel alloys can exist as FCC phases over the entire range from 0 to 100% nickel. Lunar rock magnetism research has not generally considered the implications of structures, mechanisms, crystallography, and possible interaction effects in fine particle metal. FCC metal is antiferromagnetic (? 30 wt % nickel) and would be measured in the paramagnetic component, showing a cryogenic temperature Neel point; only BCC metal would figure in the estimation of the free iron content based on saturation magnetization measurements. Evidence is presented for changes in saturation magnetization, magnetic remanence, and coercivity, and for the introduction of magnetic anisotropy when FCC metal transforms to BCC metal. From the results in the published metallurgical literature it is inferred that the induced magnetic anisotropy observed during plastic deformation of fine FCC iron precipitates in a copper matrix is associated with uniaxial development of BCC plates in the FCC precipitate. Directional impulse or any uniaxial deformation may produce magnetic anisotropy if FCC metal is made to transform to BCC metal (theγ→α _M transformation), and there will be an angular dependence for remanence acquisition, because of shape, which must be considered in paleointensity determinations. It should be noted that the transformation can be activated at any temperature below the Curie point of the BCC metal High field rotational hysteresis (Wr) has been measured in lunar fines and rocks, indicating that exchange anisotropy and/or ferromagnetic minerals with large uniaxial anisotropy exist in the lunar samples. The following are possible sources of the hysteresis:

1. Fine intergrowths of spinels or other nonequilibrium phase intergrowths developed during subsolidus reduction;
2. Fine particle intergrowths of iron and iron sulfide;
3. Iron and wustite or magnetite due to fine particle oxidation;
4. Ferromagnetic (BCC) and antiferromagnetic (FCC) metallic intergrowths.

     

Lunar rock magnetism

The relationship between the magnetization and temperature in a high constant magnetic field for a temperature range between 5 K and 1100 K was examined for Apollo 11, 12 and 14 lunar materials. The average value of Curie point temperature is (768.2 ± 3.5)°C for the lunar igneous rocks and (762.5 ± 3.4)°C for the lunar fines and breccias. A tentative conclusion about the ferromagnetic substance in the lunar materials would be that Fe is absolutely dominant with a slight association of Ni and Co, and probably Si also, in the lunar native irons.The antiferromagnetic phase of ilmenite and the paramagnetic phase of pyroxenes are considerably abundant in all lunar materials. However, a discrepancy of observed magnetization from a simulated value based on known magnetic elements for the temperature range between 10 and 40 K suggests that pyroxene phase represented by (M _x Fe_1-x ) SiO₃ (whereM = Ca²⁺, Mg²⁺, etc and 0 x 1/4) also may behave antiferromagnetically.Magnetic hysteresis curves are obtained at 5 K and 300 K, and the viscous magnetic properties also are examined for a number of lunar materials. The superparamagnetically viscous magnetization has been experimentally proven as due to fine grains of metallic iron less than 200 Å in mean diameter. The viscous magnetization is dominant in the lunar fines and breccias which is classified into Type II, while it is much smaller than the stable magnetic component in lunar igneous rocks (Type I). The superparamagnetically fine particles of metallic iron are mostly blocked at 5 K in temperature; thus coercive force (H _c ) and saturation remanent magnetization (I _R ) become much large at 5 K as compared with the corresponding values at 300 K.Strongly impact-metamorphosed parts of lunar breccias have an extremely stable NRM which could be attributed to TRM. NRM of the lunar igneous rocks and majority of breccias (or clastic rocks) are intermediately stable, but their stability is considerably higher than that of IRM of the same intensity. This result may imply that some mechanism which causes an appreciable magnitude of NRM and the higher stability, such as the shock effect, may take place on the lunar surface in addition to TRM mechanism for special cases.A particular igneous rock (Sample 14053) is found to have an unusually strong magnetism owing to a high content of metallic iron (about 1 weight percent), and its NRM amounts to 2 × 10^–3 emu/g. The abundance of such highly magnetic rocks is not known as yet but it seems that the observed magnetic anomalies on the lunar surface could be related to such highly magnetized rock masses.     

Study of the Cosmic Ray Diurnal Anisotropy During Different Solar and Magnetic Conditions

The pressure-corrected hourly counting rate data of four neutron monitor stations have been employed to study the variation of cosmic ray diurnal anisotropy for a period of about 50 years (1955–2003). These neutron monitors, at Oulu ( R _c = 0.78 GV), Deep River ( R _c = 1.07 GV), Climax ( R _c = 2.99 GV), and Huancayo ( R _c = 12.91 GV) are well distributed on the earth over different latitudes and their data have been analyzed. The amplitude of the diurnal anisotropy varies with a period of one solar cycle (∼11 years), while the phase varies with a period of two solar cycles (∼22 years). In addition to its variation on year-to-year basis, the average diurnal amplitude and phase has also been calculated by grouping the days for each solar cycle, viz. 19, 20, 21, 22, and 23. As a result of these groupings over solar cycles, no significant change in the diurnal vectors (amplitude as well as phase) from one cycle to other has been observed. Data were analyzed by arranging them into groups on the basis of the polarity of the solar polar magnetic field and consequently on the basis of polarity states of the heliosphere ( A > 0 and A < 0). Difference in time of maximum of diurnal anisotropy (shift to earlier hours) is observed during A < 0 (1970s, 1990s) polarity states as compared to anisotropy observed during A > 0 (1960s, 1980s). This shift in phase of diurnal anisotropy appears to be related to change in preferential entry of cosmic ray particles (via the helioequatorial plane or via solar poles) into the heliosphere due to switch of the heliosphere from one physical/magnetic state to another following the solar polar field reversal.     

The great-circle pattern of large circular maria: product of an earth-moon encounter

The circular maria - Orientale, Imbrium, Serenitatis, Crisium, Smythii, and Tsiolkovsky -lie nearly on a lunar great circle. This pattern can be considered the result of a very close, non-capture encounter between Moon and Earth early in solar-system history. Of critical importance in analyzing the effects of such an encounter is the position of the weightlessness limit of the Earth-Moon System which is located at about 1.63R _e, measured from the center of Earth to center of Moon. Within this weightlessness limit, material can be pulled from the lunar surface and interior by Earth's gravity and either escape from the Moon or be redistributed onto the lunar surface. In the case of an encounter with a non-spinning Moon, backfalling materials would be distributed along a lunar great circle. However, if the Moon is rotating during the encounter, the backfall pattern will deviate from the great circle, the amount depending on the rate and direction of spin. Such a close encounter model may be related to the pattern of circular maria if materials departing from the source region are visualized as spheroids of molten lunar upper mantle basalt. These spheroids, then, would impact onto the lunar surface to form a pattern of lava lakes. Radiometric dates from mare rocks are consistent with this model of mare formation if the older mare rock dates are considered to date the encounter and younger dates are considered to date subsequent volcanic eruptions on a structurally weakened Moon.     

The petrology,geochemistry, and age of lunar regolith breccias Miller Range 090036 and 090070: Insights into the crustal history of the Moon

Meteorites ejected from the surface of the Moon as a result of impact events are an important source of lunar material in addition to Apollo and Luna samples. Here, we report bulk element composition, mineral chemistry, age, and petrography of Miller Range (MIL) 090036 and 090070 lunar meteorites. MIL 090036 and 090070 are both anorthositic regolith breccias consisting of mineral fragments and lithic clasts in a glassy matrix. They are not paired and represent sampling of two distinct regions of the lunar crust that have protoliths similar to ferroan anorthosites. ⁴⁰Ar‐³⁹Ar chronology performed on two subsplits of MIL 090070,33 (a pale clast impact melt and a dark glassy melt component) shows that the sample underwent two main degassing events, one at ~3.88 Ga and another at ~3.65 Ga. The cosmic ray exposure data obtained from MIL 090070 are consistent with a short (~8–9 Ma) exposure close to the lunar surface. Bulk‐rock FeO, TiO₂, and Th concentrations in both samples were compared with 2‐degree Lunar Prospector Gamma Ray Spectrometer (LP‐GRS) data sets to determine areas of the lunar surface where the regolith matches the abundances observed on the sample. We find that MIL 090036 bulk rock is compositionally most similar to regolith surrounding the Procellarum KREEP Terrane, whereas MIL 090070 best matches regolith in the feldspathic highlands terrane on the lunar farside. Our results suggest that some areas of the lunar farside crust are composed of ferroan anorthosite, and that the samples shed light on the evolution and impact bombardment history of the ancient lunar highlands.     

Magnetochemistry of the apollo landing sites

The magnetochemical synthesis, as presented, derives from an integration of the magnetic property systematics developed with corresponding bulk chemistry and petrology, and the results of mixing and reduction responses which feature in the production of the lunar regolith. Magnetochemical properties of the lunar soils are correlated with the Al/Si ratio and telescope spectral reflectivity curves. Magnetochemical diagrams utilizingχ _p(paramagnetic susceptibility ? FeO) andI _S(saturation magnetization ? Fe metal) serve to classify lunar samples, indicate the extent of mixing, and demonstrate that although reduction does take place in production of the regolith, the role of mixing is quite significant. The relative metal size distribution and magnetic stability for various rock types and soils of varying Al/Si values are reflected in theR _I(ratio of saturation isothermal remanence-I _R, to saturation magnetization -I _S) vsR _H(ratio of remanent coercive force -H _R, to coercive force -H _C) plot. All magnetic hysteresis loop parameters considered vary systematically according to the Al/Si values. All Apollo landing sites have distinct telescope curves correlated with petrology, chemistry, Al/Si values, and magnetic properties. Magnetic properties of sites not visited can now be reasonably estimated based on telescope reflectivity curves and orbital geochemical experiments.     

Refinement of the geopotential scale factorR 0 on

Altimetric measurements of the GEOSAT satellite were used for the determination of geopotential scale factorR ₀. The geopotential valueW ₀ on the geoid surface was then computed (W ₀ =GM/R ₀).The GEOSAT Geophysical Data Records (GDR's) covering an initial period of the Exact Repeat Mission (ERM) were filtered and processed. The necessary corrections were made in order to allow a precise detection of the sea surface. Gravitational geopotential, rotation and permanent tides were taken into account and the equipotential surface which is the best approximation of the sea surface was found.The determination of the potential valueW ₀ on the mean geoid surface in this way is very promising. An associated value withW ₀ - the geopotential scale factorR ₀ - seems to be a very good Earth dimension defining quantity. Moreover, there are many possible applications ofW ₀ (R ₀) in modern geophysics.The incorporation of one of these parameters - we now recommendR ₀ - into the set of the Primary Geodetic Parameters (PGP) is discussed and suggested.     

Excess line broadening in various objects- a case for weak magnetic effects

I present updated compilations of both observational data and theoretical predictions concerning excess line width and sizes in astrophysical bodies. After removing two well-known broadening mechanisms (thermal width and width due to large scale motions such as expansion), I analyse statistically the excess line widthW _excess. The excess line width shows a changing behavior with object sizeR, of the formW _excess ~R ^q. Taking all objects together, I find thatq = 0.55 with s.d. = 0.05. This resultextends previous studies to cover 5 decades in sizes, from 0.01 pc up to 1000 pc. Taking only objects withR < 1 pc, I find thatq = 0.7 with s.d.=0.1, while taking only objects withR > 1 pc givesq = 0.5 with s.d.=0.1; thus a steeper (not flatter) value ofq at smallR may be possible. Previous claims to derive a law for objects of sizesR > 1 kpc are discussed, in relation to the problem of removing obvious large scale motions from the observed line width. Thus several models with predictedq values between 0 and 1 can be eliminated, and the remaining ones could allow weak magnetic effects on the line widths.     

Major element and primary sulfur concentrations in Apollo 12 mare basalts: The view from melt inclusions

Abstract— Major element and sulfur concentrations have been determined in experimentally heated olivine‐hosted melt inclusions from a suite of Apollo 12 picritic basalts (samples 12009, 12075, 12020, 12018, 12040, 12035). These lunar basalts are likely to be genetically related by olivine accumulation (Walker et al. 1976a, b). Our results show that major element compositions of melt inclusions from samples 12009, 12075, and 12020 follow model crystallization trends from a parental liquid similar in composition to whole rock sample 12009, thereby partially confirming the olivine accumulation hypothesis. In contrast, the compositions of melt inclusions from samples 12018, 12040, and 12035 fall away from model crystallization trends, suggesting that these samples crystallized from melts compositionally distinct from the 12009 parent liquid and therefore may not be strictly cogenetic with other members of the Apollo 12 picritic basalt suite. Sulfur concentrations in melt inclusions hosted in early crystallized olivine (Fo₇₅) are consistent with a primary magmatic composition of 1050 ppm S, or about a factor of 2 greater than whole rock compositions with 400–600 ppm S. The Apollo 12 picritic basalt parental magma apparently experienced outgassing and loss of S during transport and eruption on the lunar surface. Even with the higher estimates of primary magmatic sulfur concentrations provided by the melt inclusions, the Apollo 12 picritic basalt magmas would have been undersaturated in sulfide in their mantle source regions and capable of transporting chalcophile elements from the lunar mantle to the surface. Therefore, the measured low concentration of chalcophile elements (e.g., Cu, Au, PGEs) in these lavas must be a primary feature of the lunar mantle and is not related to residual sulfide remaining in the mantle during melting. We estimate the sulfur concentration of the Apollo 12 mare basalt source regions to be ～75 ppm, which is significantly lower than that of the terrestrial mantle.     

Occurrence and implications of secondary olivine veinlets in lunar highland breccia Northwest Africa 11273

Lunar breccias preserve the records of geologic processes on the Moon. In this study, we report the occurrence, petrography, mineralogy, and geologic significance of the observed secondary olivine veinlets in lunar feldspathic breccia meteorite Northwest Africa (NWA) 11273. Bulk‐rock composition measurements show that this meteorite is geochemically similar to other lunar highland meteorites. In NWA 11273, five clasts are observed to host veinlets that are dominated by interconnecting olivine mineral grains. The host clasts are mainly composed of mafic minerals (i.e., pyroxene and olivine) and probably sourced from a basaltic lithology. The studied olivine veinlets (~5 to 30 μm in width) are distributed within the mafic mineral host, but do not extend into the adjacent plagioclase. Chemically, these olivine veinlets are Fe‐richer (Fo_41.4–51.9), compared with other olivine grains (Fo_54.3–83.1) in lithic clasts and matrix of NWA 11273. By analogy with the secondary olivine veinlets observed in meteorites from asteroid Vesta (howardite–eucrite–diogenite group samples) and lunar mare samples, our study suggests that the newly observed olivine veinlets in NWA 11273 are likely formed by secondary deposition from a lunar fluid, rather than by crystallization from a high‐temperature silicate melt. Such fluid could be sulfur‐ and phosphorous‐poor and likely had an endogenic origin on the Moon. The new occurrence of secondary olivine veinlets in breccia NWA 11273 reveals that the fluid mobility and deposition could be a previously underappreciated geological process on the Moon.     

Bipolar outflows from stars and galaxies as a tornado phenomenon

At an early stage in the lives of stars and galaxies when they are surrounded by discs, vorticity in the disc concentrates into a central vortex, thus converting a Keplerian velocity fieldu _ø r ^–1/2 into an irrotational velocity fieldu _ør ^–1, which implies inward transfer of angular momentum. Centrifugal forces due to spin-up of the inner region and gravity dominant in the outer region then squeeze gas at intermediate layers, increasing pressure gradient in the axial direction sufficiently to drive a wide-angle low-velocity bipolar outflow from the disc. A logarithmic singularity of vorticity at the axis implies strong centrifugal forces which expand plasma to radiusR where pressure gradient balances centrifugal force density of ions; the much weaker centrifugal force density of electrons cannot balance pressure gradient, so that electrons are driven inwards relative to ions until charge separation limits the relative displacement. Now the radial gradient ofu _øcauses ions to rotate at a different rate to electrons, generating an azimuthal current densityj _øwhich is the source of an axial magnetic fieldB _zin the core of the central vortex. Centrifuging carries lines of B to the core wall, where they are wound into helical force-free configuration with B j. An annular channel of radiusR and thickness R into which parallel helical lines ofj andB are compressed constitutes a magnetic vortex tube (MVT). An MVT separates an inner high-velocity highly collimated outflow from the outer low-velocity wide-angle outflow, and is responsible for jets. Magnetic pinches in the MVT may constrict the core flow at HH objects.     

A search for a consistent model for the electromagnetic spectrum of the Crab nebula

An attempt is made to search for a consistent model to explain the electromagnetic spectrum of the Crab nebula (Tau A). It is assumed that there is a continuous injection of electrons at the centre of the nebula with an energy spectrumE ^–1.54 as evidenced by radio data. This spectrum must steepen to a slope larger than 2 at some energyE _i in order to ensure that the energy input into electrons remains finite. The spectrum must also steepen beyond an energyE _c depending on the magnetic field because of synchrotron energy losses. Two types of models are considered: Class I, in which the whole nebula is characterised by a uniform magnetic field, and Class II, in which besides the general fieldH ₀, small filamentary regions of strong fieldH _s are postulated.In models of Class I, the best fit to the observed data is obtained whenE _t >E _c andH ₀5×10^–4 gauss. However, this predicts a decrease in X-ray source size beyond 40 KeV. There are two possibilities of Class II model depending on the residence time of electrons in strong field regions being small or large. The former case explains the flattening in the optical spectrum.Experiments to distinguish between the various models are indicated.Presented at the International Conference on Cosmic Rays, Budapest, 1969.     

Evidence for a coronal magnetic bottle at 10 solar radii

The Faraday rotation of a radio source (Pioneer 6) occulted by the solar corona has been measured by Levy et al. (1969). During the course of these measurements, three large-scale transient phenomena were observed. These events were preceded by subflares and class 1 flares. These transient events are interpreted as evidence for a coronal magnetic bottle at 10 R _⊙. The velocity of propagation for the disturbance is set at 200 km/sec; the dimension of the region, 10 R _⊙; field strength at 10 R _⊙, 0.02 G; particle density, 2.0 × 10⁴/cm³; Alfvén speed, 320 km/sec. From the nature of the observations and the lack of related effects from similar flares on the interplanetary sector pattern observed at 1 AU, it is suggested that such coronal magnetic bottles expand to perhaps 10–30 R _⊙ and then contract to a few solar radii. Such a phenomena is evidence for an expansion of the corona with a sub-Alfvénic velocity. It is further suggested that such magnetic bottles may be important in the storage and diffusion of solar generated cosmic ray particles. NAS-NRC Postdoctoral Resident Research Associate.     

Primary and derived parameters of common relevance of Astronomy,Geodesy, and Geodynamics

Problem of selecting primary parameters has been discussed. Primaries should be defined uniquely, as well as, physically. Since no unique definition for semimajor axis exists, it should be replaced by the geoidal geopotential valueW ₀ or by the geopotential scale factorR ₀ =GM/W ₀, geocentric gravitational constantGM be also primary parameter. Current best estimates of some parameters are given numerically.     

Cylindrically-symmetric matter distribution with a magnetic field in Einstein-Cartan Theory

In the first part the number of independent non-vanishing components of the 3-index torsion tensorQ _jk ⁱ is reduced from 24 (in general case) to 12 — for the case of cylindrical symmetry of the underlying manifold. In the second part of the paper we have obtained an exact solution of Einstein-Cartan-Maxwell equations representing a static cylinder of perfect fluid with an axial magnetic fieldH and non-zero spin densityK.     

On the spectral reflectance and maturation darkening of lunar soils

Optical absorption and diffuse reflectance spectra were obtained for simulated lunar glasses of four different compositions, both in their as-quenched (reduced) states and following mild subsolidus oxidation. The transmission spectra, when normalized by the FeO content of the glasses, differed from one another only in the relative intensity of an unresolved band in the UV. For fixed melting conditions the strength of this band in the as-quenched glasses increased with increasing FeO, or with increasing TiO₂ for a fixed FeO content. Electron spin resonance (ESR) experiments have demonstrated the absence of Fe³⁺ or Ti³⁺ and the presence of metallic iron in these materials; all other transition-group elements were excluded in preparation. The unresolved UV absorption edge in the as-quenched reduced glasses is therefore tentatively ascribed to Fe²⁺Ti⁴⁺ intervalency charge transfer transitions. A similar UV edge was also produced by oxidation, leading to the conclusion that the assignment of this band would be ambiguous in the absence of an independent determination of the valence states of Fe and Ti. The relationship between the transmission spectra of polished samples and the reflectance spectra of sieved powders of the same materials is shown to be well described by the Kubelka-Munk approximation. Using this insight, it is possible to understand the spectral characteristics both of oxidation darkening of synthetic glass powders and of maturation darkening of lunar soils in terms of (1) the growth of the aforementioned charge transfer band(s) and (2) the development of opaque surface phases. It is shown that mechanism (1) is of primary importance in lunar highland materials and that mechanism (2) dominates in mare materials. The present results, coupled with previous findings, suggest that lunar soil maturation darkening may result from vitrification only if accompanied by (a) enrichment in the elements Fe and Ti, (b) changes in valence states of these elements, (c) partial crystallization of opaque phases such as iron, ilmenite or magnetite, or (d) a combination of (a), (b), and (c).     

Systematic Errors of High–Precision Photometric Catalogues

A very accurate imitation of Hipparcos and Tycho Hp, B _T, andV _T magnitudes was made using W, B, V, R magnitudes from the Tien Shan photometric catalogue. The calculated magnitudes were compared to the observed ones. It is shown that there are systematic differences between calculated and observed magnitudes. The systematic errors are supposed to be bound up with the sky scanning procedure on the Hipparcos satellite. Polynomials in powers of coordinates have been proposed to take into account the systematic errors. 6558 stars have been found to be appropriate high-precision photometric standards. This revised version was published online in July 2006 with corrections to the Cover Date.     

Eolian sedimentation on Earth and Mars: Some comparisons

Eolian sediments on Earth are mostly formed from quartz; they consist, in large part, of eolian sand deposits in deserts, silt and loess deposits in and adjoining present and former glaciated areas, and finally clay-sized particles carried in suspension for relatively long distances and deposited in oceanic areas by winds. The quartz particles in these regimes originally came from a granitic source; stresses in granitic rock formation, glacial action, and wind abrasion are largely responsible for making the particles available for the three kinds of eolian deposits. With respect to eolian sediments on Mars, it appears that an entirely different set of criteria must apply, but some critical parameters can usefully be compared. Evidence for free quartz on Mars is lacking and sand-sized particles are probably basaltic, although there does appear to be a deficit in the sand size range. Glacial action does not appear to be available as a large-scale particle producer but high-velocity winds could be efficient producers of very fine particles. Fine particles may aggregate in a similar way to that observed in the Australian regions where “parna” is seen; this could supply a silt mode on Mars. Impact experiments with basalt in eolian abrasion devices suggest that basalt sand-sized particles fragment rapidly to produce silt and clay-sized detritus. Cohesive forces must be more effective on Mars since the gravitational contribution to the bond/weight ratio (R) is lowe; if R = 1 at about 100 μm on Earth, then R = 1 at about 140 μm on Mars and a much greater range of deposits will be stable. Compared to the terrestrial situation, both larger and smaller particles can be expected to make significant contributions to eolian sediments on Mars. The low gravity and the high speed of moving particles and the relatively weak rock material of which they are composed will allow large-scale fine particle production.     

THE MAGNETIC INVESTIGATION OF THE SIKHOTE-ALIN IRON METEORITE SHOWER AT THE SITE OF FALL

Individual and splinter specimens of the iron meteorite shower of Sikhote-Alin and rock samples from impact craters have been studied magnetically. The results indicate that: 1) Histograms for the distribution of natural remanent magnetization J_n of individual and splinter specimens are characterized by a high correlation coefficient (0.82 ± 0.06). For the splinter specimens, a trend to an increase in number of specimens with anomalously high J_n values is observed; 2) the Earth's magnetic field did not greatly affect the magnetic properties of this iron meteorite; and 3) for rock samples taken from different craters, there was found to be a relation between the natural remanent magnetization and the energy conditions of the crater formation.     

Interaction of turbulent solar with with cometary plasma tails

The longitudinal electric field associated with the observed electrostatic turbulence in the solar wind is shown to modify the dispersive characteristics of the hydromagnetic waves propagating along the interface between the solar wind and the cometary plasma. Extremely weak turbulence has a tendency to stabilize these surface waves, whereas turbulence of moderate level can be stabilizing or destabilizing depending on the strength of the cometary magnetic fieldB _oc relative to the interplanetary magnetic fieldB _os . ForB _oc B _os , destabilization is not possible.