Peralkaline rhyolites associated with andesitic arcs of the southwest Pacific     

I.E.M. Smith  B.W. Chappell  G.K. Ward  R.S. Freeman 《Earth and Planetary Science Letters》1977,37(2):230-236

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A search for gaseous emissions from the moon     

J.W. Freeman  J.L. Benson 《Physics of the Earth and Planetary Interiors》1977,14(3):276-281

A study of 19 months of data shows that relative variations in the dayside lunar ionosphere are predictable from solar wind flux and solar extreme ultraviolet variations. Discrepancies in the absolute magnitudes exist, however. One significant discrepancy in the predicted and observed ion flux magnitudes probably arises from sputtered surface gases during and following an extended period of anomalously high solar wind flux. A second minor enhancement of the observed flux over the predicted flux may be due to endogenous lunar gas associated with an interval of high lunar seismic activity. However, considerable restraint is necessary in this interpretation since the enhancement is not strong and the interval follows within a few months after the Apollo-17 mission.  相似文献   

New Definition of Discovery for Solar System Objects     

Andrea Milani  Giovanni F. Gronchi  Zoran Knežević 《Earth, Moon, and Planets》2007,100(1-2):83-116

We propose a new formal definition of discovery for a Solar System object. It is based on an objective and mathematically rigorous algorithm to assess when a set of observations is enough to constitute a discovery. When this definition is satisfied, in almost all cases the orbit is defined well enough to establish the nature of the object discovered (Main Belt vs. Near Earth Asteroid, Trans-Neptunian vs. long period comet). The frequency of occurrence of exceptions is estimated by a set of numerical experiments. The availability of a non-subjective definition of discovery allows some rules to be adopted for the assignment of discovery credit with a minimum risk of dispute. Such rules should be fair, encourage good practice by the observers and acknowledge the contribution of the orbit computers providing the identifications and the orbits, as well as the one of all the contributing observers.  相似文献   

International viewpoint and news     

Andrea Martin  Philip E. LaMoreaux 《Environmental Geology》2007,52(6):1223-1224

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Using XMM-Newton to measure the spectrum of the Vela pulsar and its phase variation     

Armando Manzali  Andrea De Luca  Patrizia A. Caraveo 《Astrophysics and Space Science》2007,308(1-4):601-605

We report on our analysis of two XMM-Newton observations of the Vela pulsar performed in December 2000 (total exposure time: 96.5 ks). We succeeded in resolving the pulsar spectrum from the surrounding bright nebular emission taking advantage both of the accurate calibration of the EPIC point spread function and of the Chandra/HRC surface brightness map of the nebula. This made it possible to assess to pulsar spectral shape disentangling its thermal and non-thermal components. Exploiting the photon harvest, we have also been able to perform a phase-resolved study of the pulsar emission.   相似文献   

Jet Deflection by a Quasi-Steady-State Side Wind in the Laboratory     

David J. Ampleford  Andrea Ciardi  Sergey V. Lebedev  Simon N. Bland  Simon C. Bott  Jeremy P. Chittenden  Gareth N. Hall  Adam Frank  Eric Blackman 《Astrophysics and Space Science》2007,307(1-3):29-34

We present experimental data on the steady state deflection of a highly supersonic jet by a side-wind in the laboratory. The use of a long interaction region enables internal shocks to fully cross the jet, leading to the development of significantly more structure in the jet than in previous work with a similar setup (Lebedev et al., 2004). The ability to control the length of the interaction region in the laboratory allows the switch between a regime representing a clumpy jet or wind and a regime similar to a slowly varying mass loss rate. The results indicate that multiple internal oblique shocks develop in the jet and the possible formation of a second working surface as the jet attempts to tunnel through the ambient medium.  相似文献   

XMM–Newton observations of soft gamma-ray repeaters     

Sandro Mereghetti  Paolo Esposito  Andrea Tiengo 《Astrophysics and Space Science》2007,308(1-4):13-23

All the confirmed Soft Gamma-ray Repeaters have been observed with the EPIC instrument on the XMM–Newton satellite. We review the results obtained in these observations, providing the most accurate spectra on the persistent X-ray emission in the 1–10 keV range for these objects, and discuss them in the context of the magnetar interpretation.   相似文献   

3He, 20,21,22Ne, 14C, 10Be, 26Al,and 36Cl in magnetic fractions of cosmic dust from Greenland and Antarctica     

A. J. T. Jull  D. Lal  S. Taylor  R. Wieler  A. Grimberg  L. Vacher  L. R. McHargue  S. P. H. T. Freeman  C. Maden  C. Schnabel  S. Xu  R. C. Finkel  K. J. Kim  K. Marti 《Meteoritics & planetary science》2007,42(10):1831-1840

Abstract— We report on studies of the concentrations of cosmogenic nuclides in the magnetic fraction of cosmic dust particles recovered from the South Pole Water Well (SPWW) and from Greenland. Our results confirm that cosmic dust material from these locations contains measurable amounts of cosmogenic nuclides. The Antarctic particles (and possibly those from Greenland as well) also contain minor amounts of solar Ne. Concentrations of cosmogenic nuclides are consistent with irradiation of this material as small objects in space, with exposure ages similar to the expected Poynting‐Robertson (P‐R) lifetimes of 50–200 kyr for particles 25–100 μm in size.  相似文献   

First cosmogenic 10Be age constraint on the timing of Younger Dryas glaciation and ice cap thickness,western Scottish Highlands     

Nicholas R. Golledge  Derek Fabel  Jeremy D. Everest  Stewart Freeman  Steven Binnie 《第四纪科学杂志》2007,22(8):785-791

We use cosmogenic ¹⁰Be surface exposure age techniques at a locality close to Rannoch Moor, western Scottish Highlands, in order to establish the age and chronology of its most recent glaciation. Glacial erratics and an in situ bedrock quartz vein sampled from this site—the summit of Beinn Inverveigh—have yielded zero‐erosion exposure ages of 12.9 ± 1.5 ka to 11.6 ± 1.0 ka, implying complete ice cover of the mountain during the Younger Dryas, or Loch Lomond Stadial. These results fit closely with published ¹⁴C dates that bracket the maximum (lateral) extent of ice cap outlet glaciers, and are the first internally consistent ages to specifically address this period of glaciation in Scotland. Furthermore, the dates imply that previous palaeoglaciological reconstructions for this area may have underestimated both the thickness of the former ice cap and, by implication, its volume. © British Geological Survey/Natural Environment Research Council copyright 2007. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.  相似文献   

Cosmic stellar relics in the Galactic halo     

Stefania Salvadori  Raffaella Schneider  Andrea Ferrara 《Monthly notices of the Royal Astronomical Society》2007,381(2):647-662

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