A new estimate of the galactic halo mass based on the kinematics of globular clusters

We calculated the energy distribution function for globular clusters in our Galaxy, using the inversion procedure first suggested by Eddington. If the halo mass distribution is of the formM _H=r ^1.21, then the observed data on the velocity dispersion of F-clusters can be explained, resulting an enclosed mass of 4.3×10¹¹ M within a galactocentric radius of 33 kpc.     

Far-infrared emission from an intergalactic dust cloud?

We used theIRAS All Sky Maps in order to search for infrared emission in the direction of the Okroy Cloud (R.A.=12^h50^m, =22°). An enhancement of 100 m diffuse emission is evident in such a region, with an anomalous value of the ratioI _v (100 m)/A _v ; hydrogen 21 cm emission is also present with low radial speed, thus suggesting that the cloud could be a satellite of our Galaxy.     

Coastal uplift rate at Matanzas (Cuba) inferred from MIS5e phreatic overgrowths on speleothems

Many morphological elements in Cuba's landscape (e.g. marine terraces, tidal notches) demonstrate that coastal uplift has taken place, but the rate at which this occurs is not known. Carbonate phreatic overgrowths on speleothems have been found in a cave in Central North Cuba, ~1 km from the present coastline at 16 m asl. They form exceptional and unique mushroom‐shaped speleothems and balconies decorating the walls of the rooms. These phreatic overgrowths on speleothems (POS) formed at the oscillating air–water interface in sea‐level controlled anchialine lakes. U/Th dating of these overgrowths suggests ages that are compatible with the Marine Isotope Stage 5e (i.e. 130–115 ka). These POS have fixed this sea‐level highstand and demonstrate that this part of Cuba has been subjected to a much lower uplift rate than previously reported, that is, less than 0.1 mm/year since the last interglacial.     

Permineralization process promotes preservation of Holocene macrofossil charcoal in soils

The use of macrofossil soil charcoal as a palaeoecological tool to reconstruct past vegetation, climate or fire history has gained much interest in recent years. Yet little is known about taphonomy of charcoal in soils. Here we assessed the putative loss of palaeoecological information due to charcoal fragmentation after burial. We found no significant loss of charcoal mass with time. Instead, we found a significant positive relationship between the mass of charcoal particles and their age. Permineralization of charcoal particles older than ca. 5200 a explained the increased charcoal mass with time in mineral soils. The permineralization process increased the density of charcoal particles (resulting in a twofold particles mass increase) and thus offers a protection against subsequent degradation. Our results suggest high stability of palaeoecological information from charcoal macrofossils buried in mineral soils at least over the Holocene timescale. Copyright © 2011 John Wiley & Sons, Ltd.     

Validation of a chrysophyte stomatocyst‐based cold‐season climate reconstruction from high‐Alpine Lake Silvaplana,Switzerland

For the reliable assessment of past climate variability, quantitative reconstructions of seasonal temperatures are required. Currently, reconstructions of cold‐season temperatures are scarce, because most biological proxies are biased towards the growing season. Here we test the potential of chrysophyte stomatocysts (or simply ‘cysts’; siliceous resting stages of the golden‐brown algae) as a proxy for cold‐season temperature. Climate reconstructions based on biological proxies are commonly constructed using transfer functions derived from calibration in space. However, the performance of these reconstructions is rarely tested by direct comparison with meteorological data due to limitations of sample resolution or chronological control. We compare a cyst‐based near‐annual reconstruction of ‘date of spring mixing’ from the varved sediments of Lake Silvaplana (Swiss Alps) spanning AD 1870–2004 with climate variables from the same period measured at the lake shore. The high correlation between cyst‐based ‘date of spring mixing’ and cold‐season temperature demonstrates the ability of chrysophyte cysts to archive cold‐season temperature variability. Lake eutrophication, which was extensive during the last 50 years, had no obvious effect on the cyst‐based reconstruction. This study underlines the high potential of chrysophyte cysts as a quantitative proxy for cold‐season climate reconstructions. Copyright © 2011 John Wiley & Sons, Ltd.     

Self-sustained oscillations at Volcán de Colima (México) inferred by Independent Component Analysis

We have analyzed Long-Period (LP) seismic events of Volcán de Colima (Mexico) recorded by four three-component broad-band seismometers during January 2006. Frequency-domain analysis shows spectra mainly peaked in the range 0.3–2 Hz and characterized by a monotonic decreasing envelope, as those produced in a cylindrically-symmetric self-oscillating cavity interacting with a confined jet. Independent Component Analysis, a time-series decomposition method, extracts two or three nonlinear oscillation modes depending on the station, with the fundamental one peaked at 0.4–0.5 Hz. These decomposed waves have a well defined spectral content and are self-sustained oscillations with low dimensionality, as shown by dynamic system reconstruction methods. Moreover, they show radial polarization in near field and transverse polarization in far field in North-West South-East direction. Finally, we hypothesize a branched plumbing system with two principal conduits having alignments orthogonal to one another.     

Subsidence due to crack closure and depressurization of hydrothermal systems: a case study from Mt Epomeo (Ischia Island,Italy)

Levelling surveys carried out between 1990 and 2003 on the Mt Epomeo resurgent block (Ischia Island) record negative dislocations on its northern and southern flanks with a maximum subsidence rate of 1.27 cm yr⁻¹. This deformation is not associated with the cooling, crystallization or lateral drainage of magma and cannot be explained by a pressure point or prolate ellipsoid source. Results from dislocation models and the available structural and geochemical information indicate that the subsidence is due to crack closure processes along two main ENE–WSW and E–W preexisting faults, which represent the preferred pathway of CO₂ degassing from the hydrothermal system located beneath Mt Epomeo. The monitoring of the dislocations and CO₂ flux along these faults could give useful information on the dynamics of the hydrothermal system.     

Dawn Mission to Vesta and Ceres

The initial exploration of any planetary object requires a careful mission design guided by our knowledge of that object as gained by terrestrial observers. This process is very evident in the development of the Dawn mission to the minor planets 1 Ceres and 4 Vesta. This mission was designed to verify the basaltic nature of Vesta inferred both from its reflectance spectrum and from the composition of the howardite, eucrite and diogenite meteorites believed to have originated on Vesta. Hubble Space Telescope observations have determined Vesta’s size and shape, which, together with masses inferred from gravitational perturbations, have provided estimates of its density. These investigations have enabled the Dawn team to choose the appropriate instrumentation and to design its orbital operations at Vesta. Until recently Ceres has remained more of an enigma. Adaptive-optics and HST observations now have provided data from which we can begin to confidently plan the mission. These observations reveal a rotationally symmetric body with little surface relief, an ultraviolet bright point that can be used as a control point for determining the pole and anchoring a geographic coordinate system. They also reveal albedo and color variations that provide tantalizing hints of surface processes.     

Practical versus absolute salinity measurements: New advances in high performance seawater salinity sensors

Optical salinity sensors described here measure directly the seawater refractive index and thus enable a measurement of the seawater density and composition variation. We detail the measurement dependence to environmental parameters (in particular temperature and pressure) compared to conductivity sensors, and demonstrate that it may be advantageous to directly measure refractive index rather than electrical conductivity and so obtain a more direct route to density and absolute salinity.