Meteoritic material on the moon

Three types of meteoritic material are found on the Moon: micrometeorites, ancien planetesimal debris from the ‘early intense bombardment’, and debris of recent, crater-forming projectiles. Their amounts and compositions have been determined from trace element studies. The micrometeorite component is uniformly distributed over the entire lunar surface, but is seen most clearly in mare soils. It has a primitive, C1-chondrite-like composition, and comprises 1-1.5% of mature soils. Apparently it represents cometary debris. The mean annual influx rate is 2.4 × 10^?9 g cm^?2 yr^?1. It shows no detectable time variation or dependence on selenographic position. The ancient component is seen in highland breccias and soils more than 3.9 AE old. It has a fractionated composition, with volatiles depleted relative to siderophiles. The abundance pattern does not match that of any known meteorite class. At least two varieties exist (LN and DN, with Ir/Au, Re/Au 0.25-0.5 and > 0.5 the C1 value). Both seem to represent the debris of planetesimals that produced the mare basins and highland craters during the first 700 Myr of the Moon's history. It appears that the LN and DN objects impacted at less then 10 km s^?1, had diameters less than 100 km, contained more than 15% Fe, and were not internally differentiated. Both were depleted in volatiles; the LN objects also in refractories (Ir, Re). This makes it unlikely that the LN bodies served as important building blocks of the Moon. The crater-forming component has remained elusive. Only a possible hint of this component has been seen, in ejecta from Dune Crater and Apollo 12 KREEP glasses of Copernican (?) origin.     

Water use by intensively cultivated willow using estimated stomatal parameter values

Large land areas in Sweden are planned to be planted with high producing, short rotation forest stands of willow in the beginning of the 1990s. Since willow is a highly hydrophilic species, this new land use may have strong implications on water resources. To assess these implications, evaporation of Salix viminalis and Salix viminalis x caprea stands in lysimeters was analysed with the simple, yet physically realistic KAUSHA model. Parameter values for the Lohammar equation were deduced (b = 100 m³ kg^?1, k_max = 0.01 m s^?1), believed to be applicable to other sites. Simulated evaporation during the 1980 growth season for a normal stand with a production of 12 tonnes of dry matter per hectare per season was 526 mm, of which 375 mm was transpiration, 56 mm interception evaporation, and 95 mm soil evaporation. For an optimally irrigated 20-tonnes stand, the total evaporation was 584 mm, of which 430 mm was transpiration. As a comparison, Penman open water evaporation was 430 mm. To avoid soil water stress in the 20-tonnes stand, 140 mm was needed as irrigation, equivalent to 25 per cent of the mean annual precipitation. Since intensively cultivated willow plantations seemed to be using much water, it was concluded that introduction of this agri-forestry practice must be carefully planned to make use of this property, e.g. in biological filters or in reclaiming water-logged land.     

Forsterite‐rich accretionary rims around calcium‐aluminum‐rich inclusions from the reduced CV3 chondrite Efremovka

Abstract— It was suggested that multilayered accretionary rims composed of ferrous olivine, andradite, wollastonite, salite‐hedenbergitic pyroxenes, nepheline, and Ni‐rich sulfides around Allende calcium‐aluminum‐rich inclusions (CAIs) are aggregates of gas‐solid condensates which reflect significant fluctuations in physico‐chemical conditions in the slowly cooling solar nebula and grain/gas separation processes. In order to test this model, we studied the mineralogy of accretionary rims around one type A CAI (E104) and one type B CAI (E48) from the reduced CV3 chondrite Efremovka, which is less altered than Allende. In contrast to the Allende accretionary rims, those in Efremovka consist of coarse‐grained (20–40 μm), anhedral forsterite (Fa_1–8), Fe, Ni‐metal nodules, amoeboid olivine aggregates (AOAs) and fine‐grained CAIs composed of Al‐diopside, anorthite, and spinel, ± forsterite. Although the fine‐grained CAIs, AOAs and host CAIs are virtually unaltered, a hibonite‐spinel‐perovskite CAI in the E48 accretionary rim experienced extensive alteration, which resulted in the formation of Fe‐rich, Zn‐bearing spinel, and a Ca, Al, Si‐hydrous mineral. Forsterites in the accretionary rims typically show an aggregational nature and consist of small olivine grains with numerous pores and tiny inclusions of Al‐rich minerals. No evidence for the replacement of forsterite by enstatite was found; no chondrule fragments were identified in the accretionary rims. We infer that accretionary rims in Efremovka are more primitive than those in Allende and formed by aggregation of high‐temperature condensates around host CAIs in the CAI‐forming regions. The rimmed CAIs were removed from these regions prior to condensation of enstatite and alkalies. The absence of andradite, wollastonite, and hedenbergite from the Efremovka rims may indicate that these rims sampled different nebular regions than the Allende rims. Alternatively, the Ca, Fe‐rich silicates rimming Allende CAIs may have resulted from late‐stage metasomatic alteration, under oxidizing conditions, of original Efremovka‐like accretionary rims. The observed differences in O‐isotope composition between forsterite and Ca, Fe‐rich minerals in the Allende accretionary rims (Hiyagon, 1998) suggest that the oxidizing fluid had an ¹⁶O‐poor oxygen isotopic composition.     

Suggestions for some single dish radio astronomy standards

In this paper we examine the possibility of adopting standards within the context of radio astronomy and the benefits to be derived thereby. In particular we consider the application of standards within the three areas of the receiver hardware, the control and communication between different parts of the observing system, and the interface with the astronomer. The adoption of such standards will increase flexibility of observing systems, allow the easy interchange of equipment between observatories and greatly simplify guest observing. In this paper we will only consider the application of standards within the field of millimetre-wave and sub-millimetre-wave single dish astronomy. However, the principle can be easily extended to other astronomical wavebands. We describe some current developments at the Onsala Space Observatory which illustrate the proposed philosophy and show how such standards may be implemented. Naturally, the detailed definition of such standards would have to be agreed in conjunction with other interested astronomical institutions.     

Interstellar Grains in Primitive Meteorites: Diamond,Silicon Carbide,and Graphite

Abstract— Primitive meteorites contain a few parts per million (ppm) of pristine interstellar grains that provide information on nuclear and chemical processes in stars. Their interstellar origin is proven by highly anomalous isotopic ratios, varying more than 1000-fold for elements such as C and N. Most grains isolated thus far are stable only under highly reducing conditions (C/O > 1), and apparently are “stardust” formed in stellar atmospheres. Microdiamonds, of median size ～ 10 Å, are most abundant (～ 400–1800 ppm) but least understood. They contain anomalous noble gases including Xe-HL, which shows the signature of the r- and p-processes and thus apparently is derived from supernovae. Silicon carbide, of grain size 0.2–10 μm and abundance ～ 6 ppm, shows the signature of the s-process and apparently comes mainly from red giant carbon (AGB) stars of 1–3 solar masses. Some grains appear to be ≥10⁹ a older than the Solar System. Graphite spherules, of grain size 0.8–7 μm and abundance <2 ppm, contain highly anomalous C and noble gases, as well as large amounts of fossil ²⁶Mg from the decay of extinct ²⁶Al. They seem to come from at least three sources, probably AGB stars, novae, and Wolf-Rayet stars.     

ON THE DEPLETION OF MODERATELY VOLATILE ELEMENTS IN ORDINARY CHONDRITES

Within the accuracy of present data, elements of intermediate volatility (condensation temperatures between about 1100 and 600° K) do not show a correlation of abundance with volatility in equilibrated ordinary chondrites. There is no need to postulate continuous loss of gas during condensation.     

Pleistocene geomorphology and geochronology of eastern Grand Canyon: linkages of landscape components during climate changes

We report new mapping, soils, survey, and geochronologic (luminescence, U-series, and cosmogenic-nuclide) data from Pleistocene deposits in the arid setting of eastern Grand Canyon. The result is a stratigraphic framework of inset fill gravels and associated terraces that provide a record of the responses of hillslopes, tributary streams, and the Colorado River to the last 400 kyr of glacial–interglacial climate change. The best-preserved last 80 kyr of this record indicates a stratigraphic–chronologic disconnect between both deposition and incision along the Colorado River versus along the trunks of local tributaries. For example, the Colorado River finished aggrading and had already begun incising before the main pulse of aggradation in the trunks of local catchments during Marine Isotope Stage 3, and then tributary incision followed during the millennial-scale fluctuations of the last glacial epoch, potentially concurrent with mainstem aggradation. The mainstem record appears to broadly correlate with regional paleoclimate and upstream geomorphic records and thus may be responding to climatic–hydrologic changes in its mountain headwaters, with aggradation beginning during full-glacial times and continuing into subsequent interglacials. The contrasting lag time in responses of the dryland catchments within Grand Canyon may be largely a function of the weathering-limited nature of hillslope sediment supply.     

A Conceptual Schema Language for the Management of Multiple Representations of Geographic Entities

Multiple representation of geographic information occurs when a real‐world entity is represented more than once in the same or different databases. This occurs frequently in practice, and it invariably results in the occurrence of inconsistencies among the different representations of the same entity. In this paper, we propose an approach to the modeling of multiple represented entities, which is based on the relationships among the entities and their representations. Central to our approach is the Multiple Representation Schema Language that, by intuitive and declarative means, is used to specify rules that match objects representing the same entity, maintain consistency among these representations, and restore consistency if necessary. The rules configure a Multiple Representation Management System, the aim of which is to manage multiple representations over a number of autonomous federated databases. We present a graphical and a lexical binding to the schema language. The graphical binding is built on an extension to the Unified Modeling Language and the Object Constraint Language. We demonstrate that it is possible to implement the constructs of the schema language in the object‐relational model of a commercial RDBMS.     

Designing Service Architectures for Distributed Geoprocessing: Challenges and Future Directions

In this paper we study the feasibility of using services offered by a Spatial Data Infrastructure as a basis for distributed service oriented geoprocessing. By developing a prototype we demonstrate that a Spatial Data Infrastructure facilitates rapid development of applications that solve typical problems for an existing risk management application. The prototype provides users with a distributed application that enables the assessment of fire damage areas based on land cover data in a given area. The services involved in the application include: Web Feature Services, Web Map Services, a Gazetteer Service, a Catalogue Service, and Geoprocessing Services. We present the architecture of the application and describe details about implementation‐specific issues. We conclude that current OGC specifications provide a sound basis for developing service oriented architectures for geographic applications; however, in particular for geoprocessing applications, we question the feasibility of the use of Web Feature Services as data sources for larger amounts of data and call for further research in this direction.