We present observations of thermal emission from fifteen transneptunian objects (TNOs) made using the Spitzer-Space Telescope. Thirteen of the targets are members of the Classical Population: six dynamically hot Classicals, five dynamically cold Classicals, and two dynamically cold inner Classical Kuiper belt objects (KBOs). We fit out observations using thermal models to determine the sizes and albedos Of Our targets finding that the cold Classical KBOs have distinctly higher Visual albedos than the hot Classicals and other TNO dynamical classes. The cold Classicals Ire known to be distinct from other TNOs in terms of their Color distribution, size distribution, and binarity fraction. The Classical objects in our sample all have Fed colors yet they show a diversity of albedos which suggests that there is not a simple relationship between albedo and color. As a consequence of high albedos, the mass estimate of the cold Classical Kuiper belt is reduced from approximately 0.01 M-circle plus to approximately 0.001 M-circle plus. Our results also increase significantly the sample of small Classical KBOs with known albedos and sizes from 21 to 32 Such objects. (c) 2009 Elsevier Inc. All rights reserved,

We present a systematic survey for satellites of Venus using the Baade-Magellan 6.5 m telescope and IMACS wide-field CCD imager at Las Campanas observatory in Chile. In the outer portions of the Hill sphere the search was sensitive to a limiting red magnitude of about 20.4, which corresponds to satellites with radii of a few hundred meters when assuming an albedo of 0.1. In the very inner portions of the Hill sphere scattered light from Venus limited the detection to satellites of about a kilometer or larger. Although several main belt asteroids were found, no satellites (moons) of Venus were detected. (C) 2009 Elsevier Inc. All rights reserved.

The Kuiper belt is a collection of small bodies (Kuiper belt objects, KBOs) that lie beyond the orbit of Neptune and which are believed to have formed contemporaneously with the planets. Their small size and great distance make them difficult to study. KBO 55636 (2002 TX300) is a member of the water-ice-rich Haumea KBO collisional family(1). The Haumea family are among the most highly reflective objects in the Solar System. Dynamical calculations indicate that the collision that created KBO 55636 occurred at least 1 Gyr ago(2,3). Here we report observations of a multi-chord stellar occultation by KBO 55636, which occurred on 9 October 2009 UT. We find that it has a mean radius of 143 +/- 65 km (assuming a circular solution). Allowing for possible elliptical shapes, we find a geometric albedo of 0.88(0.06)(+0.15) in the V photometric band, which establishes that KBO 55636 is smaller than previously thought and that, like its parent body, it is highly reflective. The dynamical age implies either that KBO 55636 has an active resurfacing mechanism, or that fresh water-ice in the outer Solar System can persist for gigayear timescales.

The structural behavior of Al3+ in peralkaline glasses and melts along the Na2Si3O7-Na-2(NaAl)(3)O-7 join has been examined to 1200degreesC at ambient pressure with Si-29 MAS NMR and Raman spectroscopy. The distribution of Al3+ among coexisting Q(4), Q(3), and Q(2) structural units in the glasses and melts was determined as a function of bulk Al/(Al+Si) and temperature. The Al3+ resides principally in Q(4) structural units, which contain more than 70% of the total amount of Al3+. The Q(2) units contain the smallest amount of Al3+ among the Q(4), Q(3), and Q(2) structural units. There is no evidence for temperature-dependent distribution of Al3+ among the coexisting structural units at least to 1100-1200degreesC.

Cation ordering in covalent oxide glasses and melts profoundly affects the macroscopic properties, such as viscosity, diffusivity, and thermodynamic potentials. It is commonly assumed that in glasses and melts nonframework cations such as Na+, Ca2+, and Ba2+ distribute randomly around nonbridging oxygen (NBO). Several macroscopic studies on the melting of silicates and thermodynamic data have suggested that a possible nonrandomness may exist among cations around NBO in mixed-cation silicate glasses. Here, we report unambiguous experimental evidence of chemical ordering of nonframework cations and demonstrate a clear preference for certain types of cation-NBO complexes in mixed-cation silicate glasses using O-17 magic angle spinning (MAS) and multiple quantum MAS NMR. Particularly, complete bonding preference and cation ordering occurs in Ba-Mg silicate glasses (BaMgSi2O6) glass in such a way that nonbridging oxygen either only has Ba2+ as a nearest neighbor (Ba-NBO) or exists as a complex containing one Ba+ and two Mg2+ as nearest neighbors while no detectable fraction of Mg-NBO is observed. Ba-Na silicate glasses, on the other hand, show a wide distribution of configurations for two types of cations around NBO, forming Ba- and Na-NBO as well as substantial intensity of mixed NBO peaks, which indicates a prevalence of dissimilar pairs around NBO or a stronger preference to Ba-O-Si-[4] over Na-O-Si-[4]. The present results, combined with the previous results on Na-Ca silicate glasses, highlight the tendency for chemical ordering upon cation mixing in oxide glasses and may provide an atomistic explanation for diffusivity anomalies as well as activity-composition relationship of silicate melts.

Structural interaction between dissolved fluorine and silicate glass (25degreesC) and melt (to 1400degreesC) has been examined with F-19 and Si-29 MAS NMR and with Raman spectroscopy in the system Na2O-Al2O3-SiO2 as a function of Al2O3 content. Approximately 3 mol.% F calculated as NaF dissolved in these glasses and melts. From F-19 NMR spectroscopy, four different fluoride complexes were identified. These are (1) Na-F complexes (NF), (2) Na-Al-F complexes with Al in 4-fold coordination (NAF), (3) Na-Al-F complexes with Al in 6-fold coordination with F (CF), and (4) Al-F complexes with Al in 6-fold, and possibly also 4-fold coordination (TF). The latter three types of complexes may be linked to the aluminosilicate network via Al-O-Si bridges.