Extraterrestrial amino acids and L‐enantiomeric excesses in the CM2 carbonaceous chondrites Aguas Zarcas and Murchison     

Daniel P. Glavin  Jamie E. Elsila  Hannah L. McLain  Jos C. Aponte  Eric T. Parker  Jason P. Dworkin  Dolores H. Hill  Harold C. Connolly  Dante S. Lauretta 《Meteoritics & planetary science》2021,56(1):148-173

The abundances, distributions, enantiomeric ratios, and carbon isotopic compositions of amino acids in two fragments of the Aguas Zarcas CM2 type carbonaceous chondrite fall and a fragment of the CM2 Murchison meteorite were determined via liquid chromatography time‐of‐flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. A suite of two‐ to six‐carbon aliphatic primary amino acids was identified in the Aguas Zarcas and Murchison meteorites with abundances ranging from ~0.1 to 158 nmol/g. The high relative abundances of α‐amino acids found in these meteorites are consistent with a Strecker‐cyanohydrin synthesis on these meteorite parent bodies. Amino acid enantiomeric and carbon isotopic measurements in both fragments of the Aguas Zarcas meteorites indicate that both samples experienced some terrestrial protein amino acid contamination after their fall to Earth. In contrast, similar measurements of alanine in Murchison revealed that this common protein amino acid was both racemic (D ≈ L) and heavily enriched in ¹³C, indicating no measurable terrestrial alanine contamination of this meteorite. Carbon isotope measurements of two rare non‐proteinogenic amino acids in the Aguas Zarcas and Murchison meteorites, α‐aminoisobutyric acid and D‐ and L‐isovaline, also fall well outside the typical terrestrial range, confirming they are extraterrestrial in origin. The detections of non‐terrestrial L‐isovaline excesses of ~10–15% in both the Aguas Zarcas and Murchison meteorites, and non‐terrestrial L‐glutamic acid excesses in Murchison of ~16–40% are consistent with preferential enrichment of circularly polarized light generated L‐amino acid excesses of conglomerate enantiopure crystals during parent body aqueous alteration and provide evidence of an early solar system formation bias toward L‐amino acids prior to the origin of life.  相似文献   

An approach to hydrograph classification     

David M. Hannah  Barnaby P. G. Smith  Angela M. Gurnell  Glenn R. McGregor 《水文研究》2000,14(2):317-338

The stream hydrograph is an integration of spatial and temporal variations in water input, storage and transfer processes within a catchment. For glacier basins in particular, inferences concerning catchment‐scale processes have been developed from the varying form and magnitude of the diurnal hydrograph in the proglacial river. To date, however, such classifications of proglacial diurnal hydrographs have developed in a relatively subjective manner. This paper develops an objective approach to the classification of diurnal discharge hydrograph ‘shape’ and ‘magnitude’ using a combination of principal components analysis and cluster analysis applied to proglacial discharge time‐series and to diurnal bulk flow indices. The procedure is applied to discharge time‐series from two different glacier basins and four separate ablation seasons representing a gradient of increasing hydrological perturbation as a result of (i) variable water inputs generated by rainstorm activity and (ii) variable location and response of hydrological stores through a systematic decrease in catchment glacierized area. The potential of the technique for application in non‐glacial hydrological contexts is discussed. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Developing observational methods to drive future hydrological science: Can we make a start as a community?     

Keith Beven  Anita Asadullah  Paul Bates  Eleanor Blyth  Nick Chappell  Stewart Child  Hannah Cloke  Simon Dadson  Nick Everard  Hayley J. Fowler  Jim Freer  David M. Hannah  Kate Heppell  Joseph Holden  Rob Lamb  Huw Lewis  Gerald Morgan  Louise Parry  Thorsten Wagener 《水文研究》2020,34(3):868-873

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Extraterrestrial organic compounds and cyanide in the CM2 carbonaceous chondrites Aguas Zarcas and Murchison     

Jos C. Aponte  Hannah L. McLain  Danielle N. Simkus  Jamie E. Elsila  Daniel P. Glavin  Eric T. Parker  Jason P. Dworkin  Dolores H. Hill  Harold C. Connolly  Dante S. Lauretta 《Meteoritics & planetary science》2020,55(7):1509-1524

Evaluating the water‐soluble organic composition of carbonaceous chondrites is key to understanding the inventory of organic matter present at the origins of the solar system and the subsequent processes that took place inside asteroid parent bodies. Here, we present a side‐by‐side analysis and comparison of the abundance and molecular distribution of aliphatic amines, aldehydes, ketones, mono‐ and dicarboxylic acids, and free and acid‐releasable cyanide species in the CM2 chondrites Aguas Zarcas and Murchison. The Aguas Zarcas meteorite is a recent fall that occurred in central Costa Rica and constitutes the largest recovered mass of a CM‐type meteorite after Murchison. The overall content of organic species we investigated was systematically higher in Murchison than in Aguas Zarcas. Similar to previous meteoritic organic studies, carboxylic acids were one to two orders of magnitude more abundant than other soluble organic compound classes investigated in both meteorite samples. We did not identify free cyanide in Aguas Zarcas and Murchison; however, cyanide species analyzed after acid digestion of the water‐extracted meteorite mineral matrix were detected and quantified at slightly higher abundances in Aguas Zarcas compared to Murchison. Although there were differences in the total abundances of specific compound classes, these two carbonaceous chondrites showed similar isomeric distributions of aliphatic amines and carboxylic acids, with common traits such as a complete suite of structural isomers that decreases in concentration with increasing molecular weight. These observations agree with their petrologic CM type‐2 classification, suggesting that these meteorites experienced similar organic formation processes and/or conditions during parent body aqueous alteration.  相似文献   

Tuna dreams and tuna realities: Defining the term “maximising economic returns from the tuna fisheries” in six Pacific Island states     

Hannah Parris 《Marine Policy》2010

Previous work on identifying opportunities for Pacific Island countries to improve the economic returns from their tuna resources in the Western and Central Pacific Ocean (WCPO) has not generally included articulation of aspirations from Islanders themselves. However, generating such an understanding is increasingly important as these countries assert their positions in regional fisheries policy making. This study analyses the self-identified aspirations of industry and government representatives from six Pacific Island countries and finds a wider diversity of attitudes, strategies and success than is generally recognised. Implications for negotiations in the WCPFC are then discussed.  相似文献   

Constraints on Jupiters from observations of Galactic bulge microlensing events during 2000     

Yiannis Tsapras †  Keith Horne  Richard Carson  Javier Méndez Alvarez  Dan Batcheldor  Alister W. Graham  Philip A. James  Johan Knapen  Hannah Quaintrell  Ignacio Gonzalez Serrano  Peter Sorensen  Nick Wooder 《Monthly notices of the Royal Astronomical Society》2002,337(1):41-48

We present observations of eight Galactic bulge microlensing events taken with the 1.0-m Jacobus Kapteyn Telescope (JKT) on La Palma during 2000 June and July. The JKT observing schedule was optimized using a prioritizing algorithm to automatically update the target list. For most of these events we have sampled the light curves at times where no information was available from the OGLE alert team. We assume a point-source point-lens (PSPL) model and perform a maximum likelihood fit to both our data and the OGLE data to constrain the event parameters of the fit. We then refit the data assuming a binary lens and proceed to calculate the probability of detecting planets with mass ratio   q = 10⁻³  . We have seen no clear signatures of planetary deviations on any of the eight events and we quantify constraints on the presence of planetary companions to the lensing stars. For two well-observed events, 2000BUL31 and 2000BUL33, our detection probabilities peak at ∼30 and ∼20 per cent respectively for   q = 10⁻³  and   a ∼ R _E  for a  Δχ²  threshold value of 60.  相似文献   

Petrology and geochemistry of the 2014–2015 Holuhraun eruption,central Iceland: compositional and mineralogical characteristics,temporal variability and magma storage     

S?mundur?A.?HalldórssonEmail author  Enik??Bali  Margaret?E.?Hartley  David?A.?Neave  David?W.?Peate  Guemundur?H.?Guefinnsson  Ilya?Bindeman  Martin?J.?Whitehouse  Morten?S.?Riishuus  Gro?B.?M.?Pedersen  Sigureur?Jakobsson  Rob?Askew  Catherine?R.?Gallagher  Esther?R.?Guemundsdóttir  Jónas?Gudnason  William?M.?Moreland  Birgir?V.?óskarsson  Paavo?Nikkola  Hannah?I.?Reynolds  Johanne?Schmith  Thorvaldur?Thordarson 《Contributions to Mineralogy and Petrology》2018,173(8):64

The 2014–2015 Holuhraun fissure eruption provided a rare opportunity to study in detail the magmatic processes and magma plumbing system dynamics during a 6-month-long, moderate- to large-volume basaltic fissure eruption. In this contribution, we present a comprehensive dataset, including major and trace elements of whole-rock and glassy tephra samples, mineral chemistry, and radiogenic and oxygen isotope analyses from an extensive set of samples (n?=?62) that were collected systematically in several field campaigns throughout the entire eruptive period. We also present the first detailed chemical and isotopic characterization of magmatic sulfides from Iceland. In conjunction with a unique set of geophysical data, our approach provides a detailed temporal and spatial resolution of magmatic processes before and during this eruption. The 2014–2015 Holuhraun magma is compositionally indistinguishable from recent basalts erupted from the Bárðarbunga volcanic system, consistent with seismic observations for magma ascent close to the Bárðarbunga central volcano, followed by dyke propagation to the Holuhraun eruption site. Whole-rock elemental and isotopic compositions are remarkably constant throughout the eruption. Moreover, the inferred depth of the magma reservoir tapped during the eruption is consistently 8?±?5 km, in agreement with geodetic observations and melt inclusion entrapment pressures, but inconsistent with vertically extensive multi-tiered magma storage prior to eruption. The near constancy in the chemical and isotopic composition of the lava is consistent with the efficient homogenization of mantle-derived compositional variability. In contrast, occurrence of different mineral populations, including sulfide globules, which display significant compositional variability, requires a more complex earlier magmatic history. This may include sampling of heterogeneous mantle melts that mixed, crystallized and finally homogenized at mid- to lower-crustal conditions.  相似文献   

Erratum to: The Alpine nappe stack in western Austria: a crustal-scale cross section     

Hannah Pomella  Hugo Ortner  Michael Zerlauth  Bernhard Fügenschuh 《International Journal of Earth Sciences》2015,104(3):747-748

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Reactivity and temporal variability of volatile organic compounds in the Baltimore/DC region in July 2011     

Hannah S. Halliday  Anne M. Thompson  Debra W. Kollonige  Douglas K. Martins 《Journal of Atmospheric Chemistry》2015,72(3-4):197-213

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Ozone correlations between mid-tropospheric partial columns and the near-surface at two mid-atlantic sites during the DISCOVER-AQ campaign in July 2011     

Douglas K. Martins  Ryan M. Stauffer  Anne M. Thompson  Hannah S. Halliday  Debra Kollonige  Everette Joseph  Andrew J. Weinheimer 《Journal of Atmospheric Chemistry》2015,72(3-4):373-391

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