Analyses of the chondritic meteorite Orvinio (H6): Insight into the origins and evolution of shocked H chondrite material

Abstract— We have studied the petrography, reflectance spectra, and Ar‐Ar systematics of the Orivinio meteorite. Orvinio is an H chondrite not an L chondrite as sometimes reported. The material in the meteorite was involved in several impact events. One impact event produced large swaths of impact melt from H chondrite material surrounding relict clasts of chondrule‐bearing material. Not only were portions of a bulk H chondrite planestesimal melted during the impact event, but shock redistribution of metal and sulfide phases in the meteorite dramatically altered its reflectance spectra. Both the melt and relict clasts are darker than unshocked H chondrite material, bearing spectral similarities to some C‐class asteroids. Such shock metamorphism, which lowers the albedo of an object without increasing its spectral slope, may partially explain some of the variation among S‐class asteroids and some of the trends seen on asteroid 433 Eros. Noble gases record the evidence of at least two, and perhaps three, impact events in the meteorite and its predecessor rocks. The most significant evidence is for an event that occurred 600 Ma ago or less, perhaps ?325 Ma ago or less. There is also a signature of 4.2 Ga in the Ar‐Ar systematics, which could either reflect complete degassing of the rock at that time or partial degassing of even the most retentive sites in the more recent event.     

Interaction of moist convection with zonal jets on Jupiter and Saturn

Observations suggest that moist convection plays an important role in the large-scale dynamics of Jupiter's and Saturn's atmospheres. Here we use a reduced-gravity quasigeostrophic model, with a parameterization of moist convection that is based on observations, to study the interaction between moist convection and zonal jets on Jupiter and Saturn. Stable jets with approximately the same width and strength as observations are generated in the model. The observed zonal jets violate the barotropic stability criterion but the modeled jets do so only if the flow in the deep underlying layer is westward. The model results suggest that a length scale and a velocity scale associated with moist convection control the width and strength of the jets. The length scale and velocity scale offer a possible explanation of why the jets of Saturn are stronger and wider than those of Jupiter.     

A Complete Microjansky Radio Survey

The Phoenix Deep Survey is an ongoing multi-wavelength survey of a 2^° diameter field aimed at studying the properties of the sub-mJy and μJy radio population. Here, we present the latest 1.4 GHz observations of this field. The new data, reaching a 5 σ flux level of 45 μJy at the centre of a 50′ diameter field, comprise more than 700 sources with flux densities less than 1 mJy (187 of which have S_1.4 < 100 μJy). This provides one of the deepest radio (1.4 GHz) surveys currently available. The 1.4 GHz source counts are presented and show a flattening down to the 50 μJy level. At flux densities around 300 μJy there are indications that the sources detected may exhibit higher clustering than those observed at higher flux levels. This suggests that deep radio surveys could be useful for studies of large-scale structure but it also presents a warning for the representativity of sources in deep pencil-beam radio surveys. The study of the optical counterparts of the μJy population seems to indicate that the median R magnitude starts to decrease below 100 μJy. Spectroscopic classification of a sample of sources in this survey confirms the trend for an increasing fraction of star-forming galaxies over other systems down to ～ 100 μJy.     

A Comparison of Field Techniques for Confirming Dense Nonaqueous Phase Liquids

Dense nonaqueous phase liquids (DNAPLs) are immiscible fluids with a specific gravity greater than, water. When present, DNAPLs present a serious and long-term source of continued ground water and soil contamination (Pankow and Cherry 1996). Accurate characterization and delineation of DNAPL in the subsurface is critical for evaluating restoration potential and for remedy design at a site. However, obtaining accurate and definitive direct evidence of DNAPL is difficult. A field study was recently performed comparing several approaches to DNAPL characterization at a site where anecdotal and limited direct evidence of DNAPL exists. The techniques evaluated included a three-dimensional high-resolution seismic survey, field screening of soil cores with a flame ionization detector (FID)/organic vapor analyzer (OVA), hydrophobic (Sudan IV) dye-impregnated reactive FLUTe® (Flexible Liner Underground Technologies) liner material in combination with Rotasonic drill cores, centrifuged soil with Sudan IV dye, ultraviolet light (UV) fluorescence, a Geoprobe® Membrane Interface Probe (MIP®), and phase equilibrium partitioning evaluations based on laboratory analysis of soil samples. Sonic drilling provided reliable continuous cores from which minor soil structures could be evaluated and screened with an OVA, The screening provided reliable preliminary data for identifying likely DNAPL zones and for selecting samples for further analyses. The FLUTe liner material provided the primary direct evidence of the presence of DNAPL and reliable information on the thickness and nature of its occurrence (i.e., pooled or ganglia). The MIP system provided good information regarding the subsurface lithology and rapid identification and delineation of probable DNAPL areas. The three-dimensional seismic survey was of minimal benefit to this study, and the centrifuging of samples with Sudan IV dye and the use of UV fluorescence provided no benefit. Results of phase equilibrium partitioning concentration calculations for soil samples (to infer the presence of DNAPL) were in good agreement with the site screening data. Additionally, screening data compared well with previous ground water data and supported using 1% of the pure phase solubility limit of Freon 113 (2 mg/L) as an initial means to define the DNAPL study area. Based on the results of this study, the preferred approach for identifying and delineating DNAPL in the subsurface is to initially evaluate ground water data and define an area where dissolved concentrations of the target analyte(s) approach 1% of the pure phase solubility limit. Within this study area, the MIP device is used to more specifically identify areas and lithologic zones where DNAPL may have accumulated. Core samples (either Rotasonic or Geoprobe) are then collected from zones where MIP readings are indicative of the presence of DNAPL. Soil samples from the free-product portions of the core(s) are then submitted to a laboratory for positive analyte identification. Soil analyses are then combined with site-specific geotechnical information (i.e., fraction organic carbon, soil bulk density, and porosity) and equilibrium partitioning algorithms used to estimate concentrations of organic contaminants in soil samples that would be indicative of free product. Used in combination, the soil analysis and the MIP records appear to provide accurate DNAPL identification and delineation.     

A NEW CHALLENGE FOR CLIMATE STUDIES IN GEOGRAPHY

Greater emphasis is being placed on large-scale (synoptic and dynamic) climatology in geography. Concurrently, climatological research as a whole has evolved to view climate as a complex, integrated and interactive global system. In this context, we review new directions in large-scale climate studies in geography. We conclude that no matter at which climatic scale geographers are working, the new challenge is to integrate their research and teaching activities into a more holistic, global-systems approach while maintaining and improving their traditional strengths.     

A heat flow and physical properties package for the surface of Mercury

European Space Agencies fifth cornerstone mission BepiColombo includes a ‘Surface Element’ to land a scientific payload on the surface of Mercury. The current strawman payload includes a heat flow and physical properties package (HP³), focussing on key thermal and mechanical properties of the near-surface material (down to a depth of 2–5 m) and the measurement of heat flow from Mercury's interior, an important constraining parameter for models of the planet's interior and evolution. We present here an overview of the HP³ experiment package and its possible accommodation in a self-inserting ‘mole’ device. A mole is considered to be the most appropriate deployment method for HP³, at least in the currently-assumed case of an airbag-assisted soft landing architecture for the Mercury Surface Element.