FT-IR measurements of cold C3H8 cross sections at 7–15 μm for Titan atmosphere

We present absorption cross sections of propane (C₃H₈) at temperatures from 145 K to 297 K in the 690–1550 cm⁻¹ region. Pure and N₂-broadened spectra were measured at pressures from 3 Torr to 742 Torr using a Bruker IFS125 FT-IR spectrometer at JPL. The gas absorption cell, developed at Connecticut College, was cooled by a closed-cycle helium refrigerator. The cross sections were measured and compiled for individual spectra recorded at various experimental conditions covering the planetary atmosphere and Titan. In addition to the cross sections, a propane pseudoline list with a frequency grid of 0.005 cm⁻¹, was fitted to the 34 laboratory spectra. Line intensities and lower state energies were retrieved for each line, assuming a constant width. Validation tests showed that the pseudoline list reproduces discrete absorption features and continuum, the latter contributed by numerous weak and hot band features, in most of the observed spectra within 3%. Based on the pseudoline list, the total intensity in the 690–1550 cm⁻¹ region was determined to be 52.93 (±3%) × 10⁻¹⁹ cm⁻¹/(molecule cm⁻²) at 296 K; this value is within 3% of the average from four earlier studies. Finally, the merit of the pseudoline approach is addressed for heavy polyatomic molecules in support of spectroscopic observation of atmospheres of Titan and other planets. The cold cross sections will be submitted to the HITRAN database (hitran.harvard.edu), and the list of C₃H₈ pseudolines will be available from a MK-IV website of JPL (http://mark4sun.jpl.nasa.gov/data/spec/Pseudo).     

Geotechnical consequences of the Newcastle Coal Measures rocks

This paper attempts to relate the lithology and fabric of four main groups of Newcastle Coal Measures rock types to their geotechnical properties and engineering behaviour. The four groups comprise: massive sandstone and conglomerate; claystones and tuffs; mudstone, shale and siltstone; and the coal itself. Although their geological relevance is primarily concerned with underground coal mining, these rocks are exposed at the surface across most of Newcastle and its suburbs, and are thus significant in terms of urban environmental geology. The key mining issues include longwall support design and panel layouts, caving and subsidence mechanisms, soft floors and stiff roofs, water inflows and pillar design. The urban geotechnical issues include landslides and rock falls, shallow abandoned mine workings, reactive and erodible soils, waste disposal and potential sources for geomaterials.     

Charge distribution on the atmospheric aerosol over the North Atlantic and the Indian Ocean

The distribution of electric charge on the marine aerosol was determined near the sea surface of the Indian Ocean and the North Atlantic during the final stage of the Snellius II-expedition. Mean values for small ion concentrationsn ⁺=455 cm^–3 andn ^–=340 cm^–3 were found over the Atlantic, whilen ⁺=310 andn ^–=250 cm^–3 were the mean values over the Indian Ocean. The ration ⁺/n^– increased from 1.2 to 2.0 with decreasing wind velocity. At wind velocities below 5 m/s 75% of the net space charge near the ocean surface was found to be carried by small ions.     

Crustal complexity in the Lachlan Orogen revealed from teleseismic receiver functions

There is an ongoing debate about the tectonic evolution of southeast Australia, particularly about the causes and nature of its accretion to a much older Precambrian core to the west. Seismic imaging of the crust can provide useful clues to address this issue. Seismic tomography imaging is a powerful tool often employed to map elastic properties of the Earth's lithosphere, but in most cases does not constrain well the depth of discontinuities such as the Mohorovi?i? (Moho). In this study, an alternative imaging technique known as receiver function (RF) has been employed for seismic stations near Canberra in the Lachlan Orogen to investigate: (i) the shear-wave-velocity profile in the crust and uppermost mantle, (ii) variations in the Moho depth beneath the Lachlan Orogen, and (iii) the nature of the transition between the crust and mantle. A number of styles of RF analyses were conducted: H-K stacking to obtain the best compressional–shear velocity (V _P /V _S) ratio and crustal thickness; nonlinear inversion for the shear-wave-velocity structure and inversion of the observed variations in RFs with back-azimuth to investigate potential dipping of the crustal layers and anisotropy. The thick crust (up to 48 km) and the mostly intermediate nature of the crust?mantle transition in the Lachlan Orogen could be due to the presence of underplating at the base of the crust, and possibly to the existing thick piles of Ordovician mafic rocks present in the mid and lower crust. Results from numerical modelling of RFs at three seismic stations (CAN, CNB and YNG) suggest that the observed variations with back-azimuth could be related to a complex structure beneath these stations with the likelihood of both a dipping Moho and crustal anisotropy. Our analysis reveals crustal thickening to the west beneath CAN station which could be due to slab convergence. The crustal thickening may also be related to the broad Macquarie volcanic arc, which is rooted to the Moho. The crustal anisotropy may arise from a strong N–S structural trend in the eastern Lachlan Orogen and to the preferred crystallographic orientation of seismically anisotropic minerals in the lower and middle crust related to the paleo-Pacific plate convergence.     

Choppy waters ahead in “a sea of peace cooperation and friendship”?: Slow progress towards the application of maritime joint development to the East China Sea

China and Japan’s June 2008 agreement in principle on maritime cooperation in the East China Sea raised hopes of a significant breakthrough in the parties' complex and long-standing disputes in the area. Subsequent progress towards the realisation of a legally binding, formal treaty on, for example, offshore petroleum joint development has been slow to materialise. In fact, the area under dispute appears to have become more rather than less extensive. This paper examines competing maritime and sovereignty claims in the East China Sea together with progress towards maritime cooperation in the context of overlapping jurisdictional claims. The paper identifies some of the key challenges that need to be overcome in realizing a functioning joint resource management regime in the East China Sea.     

Phase relations of biotite and stilpnomelane in the greenschist facies

Phase relations of biotite and stilpnomelane and associated silicate minerals have been studied in rocks of the greenschist facies, chiefly from Otago, New Zealand and western Vermont, but also from Scotland, Minnesota-Michigan iron range, and northwest Washington. That stilpnomelane in the greenschicht facies crystallizes initially with nearly all iron in the ferrous state is indicated by chemical analyses, high p-T experiments, and phase relationships. Alteration of stilpnomelane after metamorphism not only oxidizes iron but leaches potassium; corrections for both effects must be made in using analyses of brown stilpnomelane in studies of phase relations. Two discontinuous reactions which produce biotite at the biotite isograd have been identified:

1. muscovite+stilpnomelane+actinolite→ biotite+chlorite+epidote
2. chlorite+microcline→ biotite+muscovite. Biotite produced by the first of these reactions has a limited range of variation in Fe/Mg. As grade advances within the biotite zone more magnesian and ferruginous biotites become stable in consequence of the two continuous reactions:
3. muscovite+actinolite+chlorite→ biotite (Mg-rich)+epidote
4. muscovite+stilpnomelane→ biotite (Fe-rich)+chlorite.

Stilpnomelane is stable in muscovite-free rocks throughout the biotite zone, and even up to the grade at which hornblende becomes stable. Phengitic muscovite is stable throughout the biotite zone in New Zealand and thus apparently does not contribute to the formation of biotite until a higher grade is reached.     

Coeval argon‐40/argon‐39 ages of moldavites from the Bohemian and Lusatian strewn fields

Abstract— ⁴⁰Ar/³⁹Ar ages of four tektites (moldavites) from southern Bohemia (near ?eské Budějovice, Czech Republic) and a tektite from Lusatia (near Dresden, Germany) have been determined by 11 step‐degassing experiments. The purpose of the study was to enlarge the ⁴⁰Ar/³⁹Ar data base of moldavites and to check the age relations of the Bohemian and Lusatian samples. The mean plateau‐age of the Bohemian samples, which range from 14.42 to 14.70 Ma, is 14.50 ± 0.16 (0.42) (2σ) Ma (errors in parentheses include age error and uncertainty of standard monitor age). The plateau age of the Lusatian sample of 14.38 ± 0.26 (0.44) (2σ) Ma confirms the previously published ⁴⁰Ar/³⁹Ar age of 14.52 ± 0.08 (0.40) (2σ) Ma, and demonstrates that the fall of Lusatian and Bohemian tektites were contemporaneous. Because of their geochemistry and their ages there is no doubt that the Lusatian tektites are moldavites. Accepting that moldavites are ejecta from the Nördlinger Ries impact, the new ages also date the impact event. This age is slightly younger (about 0.2–0.3 Ma) than the age suggested by earlier K‐Ar determinations.     

Aeolian abrasion and modes of fine particle production from natural red dune sands: an experimental study

A series of experiments was conducted to determine the potential for aeolian abrasion of natural dune sands to produce fine particles (< 125 µm) by (1) the release of resident fines; (2) spalling, chipping and breakage of particles; and (3) the removal of grain surface coatings. Parent samples were obtained from the surfaces of four active continental dunes and abraded using a glass ‘test tube’ chamber for up to 120 h. The fine particles produced by this abrasion process were trapped at varying time intervals and subject to detailed particle‐size analyses using a Coulter Multisizer. The abrasion of untreated parent samples produced fine particles in one of two main size classes, < 10 µm and > 50 µm, but when the parent sample was sieved to exclude particles < 250 µm, relatively more material in the range 10–50 µm was produced. For unsieved parent samples, the size range associated with the dominant mode varied according to the length of the abrasion time. The coarsest mode (> 63 µm) was dominant during the first 16 h of abrasion, then became less significant and is thought to be associated with the release of resident fines into suspension. The finest mode (< 10 µm) was absent or very weak during the first 16 h of abrasion, then became more significant and, in some instances, dominated the distribution as abrasion continued. Removal of grain surface coatings is the main source of fine material < 10 µm, and this may be a significant source of fine material in areas where sands are dominated by subrounded and rounded particles. By comparison with previous studies of aeolian particle abrasion, these natural dune sands produced very low quantities of fine material (by weight), but their spatial extent makes them potentially a significant source of dust‐sized particles at the global scale.     

Ammonia-water ice laboratory studies relevant to outer Solar System surfaces

Although water- and ammonia-ices have been observed or postulated as important components of the icy surfaces of planetary satellites in the outer Solar System, significant gaps exist in our knowledge of the spectra and behavior of such mixtures under astrophysical conditions. To that end, we have completed low-temperature spectroscopic studies (1-20 μm) of water-ammonia mixtures, with an emphasis on features in the near-IR, a region which is accessible to ground-based observations. The influences of composition, formation temperature, thermal- and radiation-processing, and phase (crystalline or amorphous) of the components were examined. Spectra of both pure NH₃ and H₂O-NH₃ icy mixtures with ratios from 0.7 to 57 were measured at temperatures from 10 to 120 K. Conditions for the formation and thermal stability of the ammonia hemihydrate (2NH₃⋅H₂O) and the ammonia monohydrate (NH₃⋅H₂O) have been examined. Band positions of NH₃ in different H₂O-ices and major band positions of the hydrates were measured. We report spectral shifts that depend on concentration and temperature. The radiation-induced amorphization of the hemihydrate was observed and the radiation destruction of NH₃ in H₂O-ices was measured. Implications of these results for the formation, stability, and detection of ammonia on outer satellite surfaces are discussed.