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[en] The lunar farside highlands problem refers to the curious and unexplained fact that the farside lunar crust is thicker, on average, than the nearside crust. Here we recognize the crucial influence of Earthshine, and propose that it naturally explains this hemispheric dichotomy. Since the accreting Moon rapidly achieved synchronous rotation, a surface and atmospheric thermal gradient was imposed by the proximity of the hot, post-giant impact Earth. This gradient guided condensation of atmospheric and accreting material, preferentially depositing crust-forming refractories on the cooler farside, resulting in a primordial bulk chemical inhomogeneity that seeded the crustal asymmetry. Our model provides a causal solution to the lunar highlands problem: the thermal gradient created by Earthshine produced the chemical gradient responsible for the crust thickness dichotomy that defines the lunar highlands
[en] The access of incident plasma to the lunar surface is dependent on the electric and magnetic fields in the vicinity. The fields and fluxes are mutually dependent: the magnetic fields (local and external) gate the access of the external plasma to the surface, and the particle flux that reaches the surface affects the current balance with surface photoelectrons, which in turn determines the surface potential. As the electrons in the incident plasma are deflected more severely than the ions by the lunar fields, a charge separation layer occurs. Thus another electric field is created to equalize the penetrating fluxes of electrons and protons. The deflection of the incident protons and electrons in opposite ways creates a current that changes the local magnetic field slightly. A complete self-consistent theoretical model of fields and fluxes is dependent on a number of factors (electron and proton temperatures and densities, plasma flow velocity, external magnetic field orientation and magnitude, and the characteristics of any local fields) and is beyond the scope of this thesis. This thesis calculates open and shadow zones for the access of incident particles to the surface as a function of the external magnetic-field direction, both for the case of no local magnetic field and for the large local magnetic field estimated at the Apollo 14 ASLEP site. Predictions are made for the variation of the magnitude of the charge-separation electric field with variable external plasma and field conditions. These open and shadow zones and their effect on the surface potential are tested and confirmed with particle data from the Apollo 14 CPLEE plasma analyzer and magnetic-field data from Explorer 35 in lunar orbit
[en] Approximately 500 glasses between 1 mm and 125 μm in size have been analyzed from fourteen samples from the Apollo 16 core sections 60002 and 60004. The majority of glasses have compositions comparable to those found in previous studies of lunar surface soils: however, two new and distinct glass compositions that are probably derived in part from mare material occur in the core samples. The major glass composition in all samples is that of Highland Basalt glass, but it also appears that high-K Fra Mauro Basalt (KREEP) glass is more common at the Apollo 16 site than was previously thought. The relative abundance of glasses within the core samples is random in distributions each sample is characterized by a particular assemblage and distribution of the constituent glass compositions. (Auth.)
[en] Chemical and isotopic analyses of various grainsize fractions of lunar soils show the presence of an 'exotic component' in practically all lunar soils. The patterns of enrichments in the grain-size fractions and the Sr-isotopic data show that the regolith evolution displays the combined effects of comminution of local rock types and addition of the exotic component. The chemical characteristics of this exotic component as deduced from the chemical and isotopic data in soils from Apollo 11, 12, 15 and 16 uniformly point to compositions similar to the material from Fra Mauro region collected in the Apollo 14 mission. There is a strong correlation between the amount of exotic component in a soil and its distance from the Fra Mauro region. It is suggested that the exotic component represents trace element enriched material from the Imbrium-Procellarum region, which was surficially deposited during Imbrium excavation and re-exposed from under the mare-lavas in subsequent cratering events. Surficial transport processes have distributed these materials widely over the lunar surface. There appears no need to invoke a global radioactive crust on the Moon nor of 'hot spots' distributed over the entire surface of the Moon to explain the ubiquitous presence of this component in lunar regolith, nor is there a compelling reason at present to postulate a global melting process for the generation of highly differentiated materials such as 'kreep' and the exotic component. (author)
[en] ISEE-3 measurements indicate that a broad mantle-like boundary layer plasma often exists within the distant geomagnetic tail lobes at all latitudes, directly adjacent to the tail magnetopause. The presence of this boundary layer at large tail distances indicates that plasma from the magnetosheath often crosses the magnetopause locally along much of the length of the tail, and is evidence that the tail is ''open.''
[en] A simplified method to model lunar resonance spin-orbital interaction is developed for numerical integration by which orbital equations are integrated separately from rotational ones; however, no fictions secular perturbations arise in the longitude or node. (author). 2 figs., 3 refs
[en] Using recent determinations of the atomic and tidal lunar acceleration, we propose a model to evaluate q-bar0. Our conclusion is that the universe is open for values of H0 close to 50 km s-1 Mpc-1
[en] Parallax is the most fundamental technique for measuring distances to astronomical objects. Although terrestrial parallax was pioneered over 2000 years ago by Hipparchus (ca. 140 B.C.E.) to measure the distance to the Moon, the baseline of the Earth is so small that terrestrial parallax can generally only be applied to objects in the Solar System. However, there exists a class of extreme gravitational microlensing events in which the effects of terrestrial parallax can be readily detected and so permit the measurement of the distance, mass, and transverse velocity of the lens. Here we report observations of the first such extreme microlensing event OGLE-2007-BLG-224, from which we infer that the lens is a brown dwarf of mass M = 0.056 ± 0.004 M sun, with a distance of 525 ± 40 pc and a transverse velocity of 113 ± 21 km s-1. The velocity places the lens in the thick disk, making this the lowest-mass thick-disk brown dwarf detected so far. Follow-up observations may allow one to observe the light from the brown dwarf itself, thus serving as an important constraint for evolutionary models of these objects and potentially opening a new window on substellar objects. The low a priori probability of detecting a thick-disk brown dwarf in this event, when combined with additional evidence from other observations, suggests that old substellar objects may be more common than previously assumed.