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

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.     

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

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.     

A double spike for osmium analysis of highly radiogenic samples

Geologic samples containing highly radiogenic Os (molybdenites and low-level, highly radiogenic (LLHR) samples) have no internal means by which to correct for mass fractionation during isotopic measurement by mass spectrometry. We describe a double spike for use with highly radiogenic samples, created by combining isotopically enriched ¹⁸⁸Os and ¹⁹⁰Os. Spiking molybdenite and other highly radiogenic minerals with this tracer allows for a fractionation correction, as well as a more reliable determination of common Os relative to analysis using single spikes.

The precise isotopic composition of the double spike is determined by a calibration against natural Os, in which two separate measurements are necessary: one each for the pure double spike and the spike–standard mixture. An estimate of the true composition of the spike is obtained by least squares approximation, and the errors are obtained by Monte Carlo methods. Sample analyses are then much more straightforward than the calibration because isotopic compositions of all components are known a priori.

Results obtained with a mixed Re-double Os spike demonstrate an improved reproducibility over individual ¹⁸⁵Re and ¹⁹⁰Os spikes. For an Archean in-house molybdenite standard we now observe a reproducibility of 0.08%. The ability to make a fractionation correction is essential for Os measurements made by ion counting. With the double Os spike, young samples and those with low Re contents (i.e., LLHR) can now be accurately analyzed. The ¹⁸⁸Os–¹⁹⁰Os double spike also allows a determination of the common Os contents of highly radiogenic samples. Common Os is poorly determined for ancient samples with high concentrations of ¹⁸⁷Os, which fortunately are not sensitive to estimates of common Os. Common Os can be reasonably well determined for younger samples and those with low Re contents. We report a common Os concentration of 0.4±0.1 ppb for an 11 Ma molybdenite. Consideration of common Os content is important for age determination of young samples and LLHR samples, and is not possible by other published means of Os analysis.     

Local Perceptions of the Sustainability of Alaska’s Highly Contested Cook Inlet Salmon Fisheries

Using a mixed set of ethnographic methods including interviews and a structured survey, we evaluate local perceptions about the sustainability of salmon fisheries among fishers of the Cook Inlet region of Alaska. A majority of residents report participating in these fisheries, but we find significant disagreement about their sustainability. Household income and the types of fishing practiced both influence people's responses, and many implicated specific user groups for overharvesting and/or for receiving unfair catch allocations. Drawing on the theoretical areas of information theory and political ecology, we argue that these findings reveal a complex interplay among the practical, social, and political aspects of how local resource users, or “local experts,” develop and communicate their assessments of ecological conditions in a context of conflict. We conclude with notes on future research as it relates to the successful design of local-management and co-management solutions, especially in settings where resources are contested by stakeholders.     

A polyphase glacitectonic model for ice-marginal retreat and terminal moraine development: the Middle Pleistocene British Ice Sheet,northern Norfolk,UK

Recent investigations from modern environments demonstrate that many terminal moraines do not simply record a single glacial maximum, but instead reveal a complex oscillatory pattern of ice-marginal behaviour including polyphase retreat. Within this study, we examine the geomorphology, geology and internal structure of a terminal moraine complex – the ‘Cromer Ridge’ in north Norfolk to reconstruct patterns of ice-marginal behaviour. Previously, this landform was interpreted as the limit of a southern extension of the British Ice Sheet during a Middle Pleistocene glaciation. Evidence presented here reveals a more complicated pattern of ice-marginal behaviour with the ‘Cromer Ridge’ reinterpreted as a ‘complex’ comprising several ridge elements. We propose that the maximum ice extent lay further to the south, with the size and morphology of the largest ridge element (the ‘Cromer Ridge’ as previously defined) a facet of thrust-stacking at an ice-marginal still-stand. We recognise multiple oscillations of the ice-front recorded against a twelve-stage model for the decay of the southern margins of a fast-flowing lobe of North Sea ice. Changes in ice-marginal dynamics are identified by the superimposition and lateral and vertical evolution of glacitectonic styles. Differences between these various states, and switches between ‘shallow’ and ‘deep’ thin-skinned glacitectonics, are strongly influenced by sub-marginal and proglacial water availability. Examination of the evidence for the morphostratigraphic proposals for the glacitectonic assemblage, within the context of the above interpretation, suggests that many of the ‘glacigenic landforms’ are erosional and a MIS 12 age of formation is favoured although several anomalies remain to be explained.     

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

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.