Evolution of carbonaceous chondrite parent bodies: Insights into cometary nuclei

It is thought that cometary samples will comprise the most primitive materials that are able to be sampled. Although parent body alteration of such samples would not necessarily detract from scientists' interest in them, the possibility exists that modification processes may have affected cometary nuclei. Inferences about the kinds of modifications that might be encountered can be drawn from data on the evolution of carbonaceous chondrite parent bodies. Observations suggest that, of all the classes of chondrites, these meteorites are most applicable to the study of comets. If the proportion of possible internal heat sources such as Al-26 in cometary materials are similar to those in chondrites, and if the time scale of comet accretion was fast enough to permit incorporation of live radionuclides, comets might have had early thermal histories somewhat like those of carbonaceous chondrite parent bodies

Modal abundances of CAIs: Implications for bulk chondrite element abundances and fractionations

Modal abundances of Ca,Al-rich inclusions (CAIs) are poorly known and reported data scatter across large ranges. We combine reported CAI modal abundances and our own set, and present a complete list of CAI modal abundances in carbonaceous chondrites. This includes (in area%): CV: 2.98, CM: 1.21, Acfer 094: 1.12, CO: 0.99, CK/CV (Ningqiang & DaG 055): 0.77, CK: 0.2, CR: 0.12 and CB: 0.1. CAIs are Poisson distributed and if only small areas (<1000 mm2) are studied, the data are probably not representative of the true CAI modal abundances, explaining their reported large scatter in a single chondrite group. Carbonaceous chondrites have excess bulk Al concentrations when compared to the CI-chondritic value. We find a correlation between this excess and CAI modal abundances and conclude that the excess Al was delivered by CAIs. The excess Al is only a minor fraction (usually ~10 rel%, but 25 rel% in case of CVs) of the bulk chondrite Al and cannot have contributed much 26Al to heat the chondrite parent body. Ordinary, enstatite, R- and K-chondrites have an Al deficit relative to CI chondrites and only very low CAI modal abundances, if any are present at all. Carbonaceous chondrites also had an initial Al deficit if the contribution of Al delivered by CAIs is subtracted. Therefore all chondrites probably lost a refractory rich high-T component. Only minor amounts of CAIs are present in the matrix or have been present in the chondrule precursor aggregates. Most CAI size distributions contain more than one size population, indicating that CAIs from within a single meteorite group had different origins.Comment: Meteoritics & Planetary Sciences (in press

What we know about Mars (but otherwise wouldn't) if it is the shergottite parent body

The evidence that some meteorites may actually be samples of fairly large solar system bodies, specifically the moon and the planet Mars was presented. The proposed martian meteorites, called shergottites are igneous rocks that crystallized from molten magmas. Their crystallization ages are much too young to have formed by internal melting within small asteroids, and the unusual chemical composition of gases trapped when these rocks were severely shocked matches that of the martin atmosphere measured by Viking. The implications of these samples for martian evolution was discussed and suggested, that if Mars is the shergottite parent body, the martian interior is much more like that of the earth than has been previously thought. Shergottites explain presence of small magnetic field indicate that volatileement concentratins in Mars should be similar to the Earth, and explain the great lengths of volcanic flows on the martian surface

Comparison of Archean and Phanerozoic granulites: Southern India and North American Appalachians

Archean granulites at the southern end of the Dharwar craton of India and Phanerozoic granulites in the southern Appalachians of North America share an important characteristic: both show continuous transitions from amphibolite facies rocks to higher grade. This property is highly unusual for granulite terranes, which commonly are bounded by major shears or thrusts. These two terranes thus offer an ideal opportunity to compare petrogenetic models for deep crustal rocks formed in different time periods, which conventional wisdom suggests may have had different thermal profiles. The salient features of the Archean amphibolite-to-granulite transition in southern India have been recently summarized. The observed metamorphic progression reflects increasing temperature and pressure. Conditions for the Phanerozoic amphibolite-to-granulite transition in the southern Appalachians were documented. The following sequence of prograde reactions was observed: kyanite = sillimanite, muscovite = sillimanite + K-feldspar, partial melting of pelites, and hornblende = orthopyroxene + clinopyroxene + garnet. The mineral compositions of low-variance assemblages in mafic and intermediate rocks are almost identical for the two granulite facies assemblages. In light of their different fluid regimes and possible mechanisms for heat flow augmentation, it seems surprising that these Archean and Phanerozoic granulite terranes were apparently metamorphosed under such similar conditions of pressure and temperature. Comparison with other terrains containing continuous amphibolite-to-granulite facies transitions will be necessary before this problem can be addressed

Basalt-trachybasalt samples in Gale Crater, Mars

The ChemCam instrument on the Mars Science Laboratory (MSL) rover, Curiosity, observed numerous igneous float rocks and conglomerate clasts, reported previously. A new statistical analysis of single-laser-shot spectra of igneous targets observed by ChemCam shows a strong peak at ~55 wt% SiO2 and 6 wt% total alkalis, with a minor secondary maximum at 47–51 wt% SiO2 and lower alkali content. The centers of these distributions, together with the rock textures, indicate that many of the ChemCam igneous targets are trachybasalts, Mg#=27 but with a secondary concentration of basaltic material,with a focus of compositions around Mg#=54. We suggest that all of these igneous rocks resulted from low-pressure, olivine-dominated fractionation of Adirondack (MER) class-type basalt compositions. This magmatism has subalkaline, tholeiitic affinities. The similarity of the basalt endmember to much of the Gale sediment compositions in the first 1000 sols of the MSL mission suggests that this type of Fe-rich, relatively low-Mg#, olivine tholeiite is the dominant constituent of the Gale catchment that is the source material for the fine-grained sediments in Gale. The similarity to many Gusev igneous compositions suggests that it is a major constituent of ancient Martian magmas, and distinct from the shergottite parental melts thought to be associated with Tharsis and the Northern Lowlands. The Gale Crater catchment sampled a mixture of this tholeiitic basalt along with alkaline igneous material, together giving some analogies to terrestrial intraplate magmatic provinces

An economic analysis of the production and marketing of floricultural crops in Tennessee

The primary objective of this analysis was to provide Tennessee green industry farmers with information on the production and marketing of floriculture crops. An overview of U.S. national, southern regional and Tennessee green industry production and marketing characteristics was presented to describe the general production and marketing environment in which green industry farms operate. A mail survey of Tennessee greenhouses was conducted in 1994 and the data received from 83 greenhouses was analyzed to describe specific production and marking activities among these farmers. The survey responses were stratified and compared according to greenhouse size in square feet, gross annual sales and region within Tennessee. Chi-square tests were used to determine the significance of the results. Overall, greenhouse managers reported a total of 2.7 million square feet under greenhouse cover during the 1993 production period and 29.3 percent of managers planned to expand the size of their operations within the next two years. On average greenhouses employed 6.9 permanent employees and family members were an important source of labor among all strata of greenhouse operations. Among all survey strata, greenhouses were most commonly constructed of double layer poly covering. Managers indicated a variety of current production technologies with larger firms generally using a wider variety of technologies to perform specific production tasks than did the smaller firms. Computerization was the most commonly reported technology adoption planned by managers within the next five years. Retail sales accounted for the largest proportion of greenhouse market activity and, overall, the largest proportions of greenhouse advertising budgets were allocated to newspaper and radio advertising. Television was also an important advertising medium. Bedding plants contributed the largest proportion of annual sales although the sale of these plants was highly seasonal and confined primarily to the months of April and December

Formula timing from the standpoint of investment

Thesis (M.B.A.)--Boston Universit

The Function and Regulon of Transcription Factor RcsA in \u3ci\u3ePantoea\u3c/i\u3e sp. YR343

Plants have a microbiome that hosts a variety of microorganisms, including pathogenic, neutral, and beneficial bacterial strains. These strains can influence the plant’s growth and health. Determining how the microbiome is recruited and structured and how these microbes communicate and interact with each other is needed to understand, and, ultimately, manipulate the effect of the microbiome on plant health. In order to pursue this goal, we are studying the plant-associated microbe Pantoea sp. YR343. Pantoea sp. YR343 is a motile and rod-shaped bacterium isolated from the roots of Populus deltoides- a promising source for biofuels. It possesses the ability to solubilize phosphate as well as produce the phytohormone indole-3-acetic acid (IAA). Moreover, Pantoea sp. YR343 shows both swimming and swarming motility, is a robust root colonizer, and induces lateral root production in Arabidopsis thaliana and Populus deltoides. As part of a genetic screen to identify factors that promote root colonization, we identified a transposon mutant that mapped to a gene encoding the transcription regulator RcsA. The transposon mutant displayed defects in biofilm formation, capsule production, and colonization of wheat roots, suggesting that it may influence the ability of Pantoea sp. YR343 to associate with plants. Understanding the function of this gene in Pantoea sp. YR343 provides insights into the regulation and mechanisms of plant association

Light stable isotope analysis of meteorites by ion microprobe

The main goal was to develop the necessary secondary ion mass spectrometer (SIMS) techniques to use a Cameca ims-4f ion microprobe to measure light stable isotope ratios (H, C, O and S) in situ and in non-conducting mineral phases. The intended application of these techniques was the analysis of meteorite samples, although the techniques that have been developed are equally applicable to the investigation of terrestrial samples. The first year established techniques for the analysis of O isotope ratios (delta O-18 and delta O-17) in conducting mineral phases and the measurement of S isotope ratios (delta S-34) in a variety of sulphide phases. In addition, a technique was developed to measure delta S-34 values in sulphates, which are insulators. Other research undertaken in the first year resulted in SIMS techniques for the measurement of wide variety of trace elements in carbonate minerals, with the aim of understanding the nature of alteration fluids in carbonaceous chondrites. In the second year we developed techniques for analyzing O isotope ratios in nonconducting mineral phases. These methods are potentially applicable to the measurement of other light stable isotopes such as H, C and S in insulators. Also, we have further explored the analytical techniques used for the analysis of S isotopes in sulphides by analyzing troilite in a number of L and H ordinary chondrites. This was done to see if there was any systematic differences with petrological type