137Cesium and other contaminants have leaked from single-shell storage tanks (SSTs) into coarse-textured, relatively unweathered unconsolidated sediments. Contaminated sediments were retrieved from beneath a leaky SST to investigate the distribution of adsorbed 137Cs+ across different sediment size fractions. All fractions contained mica (biotite, muscovite, vermiculatized biotite), quartz, and...

We investigate the relationship between the petrology and visible–near infrared spectra of the unbrecciated eucrites and synthetic pyroxene–plagioclase mixtures to determine how spectra obtained by the Dawn mission could distinguish between several models that have been suggested for the petrogenesis of Vesta’s crust (e.g., partial melting and magma ocean). Here, we study the spectra of petrolo...

[1] Complete sets of mineral abundances for relatively unaltered volcanic or volcaniclastic rocks in Gusev Crater have been determined by modeling Mössbauer subspectral areas as mineral weight percentages, and combining those percentages with the proportions of iron-free minerals not detected by Mössbauer (normative plagioclase, apatite, and chromite, as calculated from Alpha Particle X-Ray Spe...

The sharp, nonoverlapping Raman bands for plagioclase, pyroxene, and olivine would be advantageous for on-surface, active mineralogical nalysis of lunar materials. A robust, light-weight, low-power, over-based Raman spectrometer with a laser exciting source, entirely transmission-mode holographic optics, and a charge-coupled device (CCD) detector could fit within a <20 cm cube. A sensor head on...

The transition from 41to 100-kyr glacial cycles and concomitant increase in global ice volume ~1 Ma remain an enigmatic feature of late Cenozoic climate. Here, we examine the petrology, mineralogy, and geochemistry of the silicate fraction of tills spanning the past 2 Ma from the north-central United States to evaluate the hypothesis that this so-called middle Pleistocene transition (MPT) occur...

The size of the Mercurian core and the low ferrous iron bearing silicate content of its crust offer constraints on formation models for the planet. Here we consider a bulk composition that allows endogenous formation of the planet's large core, and by processing the mantle through a magma ocean, would produce a low-iron crust. More Earth-like bulk compositions require silicate removal, perhaps ...

Introduction: The Martian origin of the group of SNCO’s comprising now 16 different meteorites is widely accepted [1]. The ejection of these meteorites from Mars requires an impact process which necessarily involves a certain level of shock metamorphism affecting the meteorites to get accelerated to Martian escape velocity. Previous studies [2 and ref. in 1] clearly showed that all 16 Martian m...

Viscosity has been determined during isothermal crystallization of an andesite from Tungurahua volcano (Ecuador). Viscosity was continuously recorded using the concentric cylinder method and employing a Pt-sheathed alumina spindle at 1 bar and from 1400°C to subliquidus temperatures to track rheological changes during crystallization. The disposable spindle was not extracted from the sample but...

A spectacular example of columnar-jointed basalt occurs at Svartifoss in the Vatnajökull National Park of southern Iceland. The columns are notable for a variety of features on the vertical joint surfaces and the horizontal parting surfaces. The jointed surfaces of the columns display horizontal striations at a spacing of centimeters to decimeters. The individual striations exhibit crescentic h...

The conventional K-Ar dating method was applied to the 1986 dacite flow from the new lava dome at Mount St. Helens, Washington. Porphyritic dacite which solidified on the surface of the lava dome in 1986 gives a whole rock K-Ar “age” of 0.35±0.05 million years (Ma). Mineral concentrates from the dacite which formed ins 1986 give K-Ar “ages” from 0.34±0.06 Ma (feldspar-glass concentrate) to 2.8±...