Io’s atmosphere: Constraints on sublimation support from density variations on seasonal timescales using NASA IRTF/TEXES observations from 2001 to 2010

We present an analysis of 19 μm spectra of Io’s SO₂ atmosphere from the TEXES mid-infrared high spectral resolution spectrograph on NASA’s Infrared Telescope Facility, incorporating new data taken between January 2005 and June 2010 and a re-analysis of earlier data taken from November 2001 to January 2004. This is the longest set of contiguous observations of Io’s atmosphere using the same instrument and technique thus far. We have fitted all 16 detected blended absorption lines of the ν₂ SO₂ vibrational band to retrieve the subsolar values of SO₂ column abundance and the gas kinetic temperature. By incorporating an existing model of Io’s surface temperatures and atmosphere, we retrieve sub-solar column densities from the disk-integrated data. Spectra from all years are best fit by atmospheric temperatures <150 K. Best-fit gas kinetic temperatures on the anti-Jupiter hemisphere, where SO₂ gas abundance is highest, are low and stable, with a mean of 108 (±18) K. The sub-solar SO₂ column density between longitudes of 90–220° varies from a low of 0.61 (±0.145) × 10^?17 cm^?2, near aphelion in 2004, to a high of 1.51 (±0.215) × 10¹⁷ cm^?2 in 2010 when Jupiter was approaching its early 2011 perihelion. No correlation in the gas temperature was seen with the increasing SO₂ column densities outside the errors.Assuming that any volcanic component of the atmosphere is constant with time, the correlation of increasing SO₂ abundance with decreasing heliocentric distance provides good evidence that the atmosphere is at least partially supported by frost sublimation. The SO₂ frost thermal inertias and albedos that fit the variation in atmospheric density best are between 150–1250 W m^?2 s^?1/2 K^?1 and 0.613–0.425 respectively. Photometric evidence favors albedos near the upper end of this range, corresponding to thermal inertias near the lower end. This relatively low frost thermal inertia produces larger amplitude seasonal variations than are observed, which in turn implies a substantial additional volcanic atmospheric component to moderate the amplitude of the seasonal variations of the total atmosphere on the anti-Jupiter hemisphere. The seasonal thermal inertia we measure is unique both because it refers exclusively to the SO₂ frost surface component, and also because it refers to relatively deep subsurface layers (few meters) due to the timescales of many years, while previous studies have determined thermal inertias at shallower levels (few centimeters), relevant for timescales of ～2 h (eclipse) or ～2 days (diurnal curves).     

Investigating the redox sensitivity of para-toluenesulfonamide (p-TSA) in groundwater

The groundwater downstream of a former sewage irrigation farm in Berlin is contaminated with ammonium (NH₄ ⁺) and para-toluenesulfonamide (p-TSA), besides other anthropogenic pollutants. In the field, in situ removal of NH₄ ⁺ by gaseous oxygen (O₂) and air injection is currently being tested. A laboratory column experiment using aquifer material and groundwater from the site was performed to determine whether this remediation technology is also feasible to reduce high p-TSA concentrations in the anoxic groundwater. First, the column was operated under anoxic conditions. Later, compressed air was introduced into the system to simulate oxic conditions. Samples were collected from the column outlet before and after the addition of compressed air. The experiment revealed that whereas p-TSA was not removed under anoxic conditions, it was almost fully eliminated under oxic conditions. Results were modelled using a transient one-dimensional solute transport model. The degradation rate constants for p-TSA increased from 2.8E−06 to 7.5E−05 s^–1 as a result of microbial adaption to the change of redox conditions. Results show that O₂ injection into an anoxic aquifer is a successful strategy for p-TSA remediation.     

Large wood budget and transport dynamics on a large river using radio telemetry

Despite the abundance of large wood (LW) river studies there is still a lack of understanding of LW transport dynamics on large low gradient rivers. This study used 290 radio frequency identification tagged (RFID) LW and 54 metal (aluminum) tagged LW, to quantify the percent of in‐channel LW that moves per year and what variables play a role in LW transport dynamics. Aluminum tags were installed and monitored on LW in‐transit during the rising limb of a flood, the mean distance traveled by those pieces during the week was 13.3 river kilometers (km) with a maximum distance of 72 km. RFID tagged LW moved a mean of 11.9 km/yr with a maximum observed at 101.1 km/yr. Approximately 41% of LW low on the bank moves per year. The high rate of transport and distance traveled is likely due to the lack of interaction between LW floating in the channel and the channel boundaries, caused primarily by the width of the channel relative to length of the LW. Approximately 80% of the RFID tags moved past a fixed reader during the highest 20% of river stage per year. LW transport and logjam dynamics are complicated at high flows as pieces form temporary jams that continually expand and contract. Unlike most other studies, key members that create a logjam were defined more by stability than jam size or channel/hydrologic conditions. Finally, using an existing geomorphic database for the river, and data from this study, we were able to develop a comprehensive LW budget showing that 5% of the in‐channel LW population turns over each year (input from mass wasting and fluvial erosion equals burial, decomposition, and export out of system) and another 16% of the population moving within the system. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

Silicon isotopic fractionation of CAI-like vacuum evaporation residues

Calcium-, aluminum-rich inclusions (CAIs) are often enriched in the heavy isotopes of magnesium and silicon relative to bulk solar system materials. It is likely that these isotopic enrichments resulted from evaporative mass loss of magnesium and silicon from early solar system condensates while they were molten during one or more high-temperature reheating events. Quantitative interpretation of these enrichments requires laboratory determinations of the evaporation kinetics and associated isotopic fractionation effects for these elements. The experimental data for the kinetics of evaporation of magnesium and silicon and the evaporative isotopic fractionation of magnesium is reasonably complete for Type B CAI liquids (Richter F. M., Davis A. M., Ebel D. S., and Hashimoto A. (2002) Elemental and isotopic fractionation of Type B CAIs: experiments, theoretical considerations, and constraints on their thermal evolution. Geochim. Cosmochim. Acta66, 521-540; Richter F. M., Janney P. E., Mendybaev R. A., Davis A. M., and Wadhwa M. (2007a) Elemental and isotopic fractionation of Type B CAI-like liquids by evaporation. Geochim. Cosmochim. Acta71, 5544-5564.). However, the isotopic fractionation factor for silicon evaporating from such liquids has not been as extensively studied. Here we report new ion microprobe silicon isotopic measurements of residual glass from partial evaporation of Type B CAI liquids into vacuum. The silicon isotopic fractionation is reported as a kinetic fractionation factor, α_Si, corresponding to the ratio of the silicon isotopic composition of the evaporation flux to that of the residual silicate liquid. For CAI-like melts, we find that α_Si = 0.98985 ± 0.00044 (2σ) for ²⁹Si/²⁸Si with no resolvable variation with temperature over the temperature range of the experiments, 1600-1900 °C. This value is different from what has been reported for evaporation of liquid Mg₂SiO₄ (Davis A. M., Hashimoto A., Clayton R. N., and Mayeda T. K. (1990) Isotope mass fractionation during evaporation of Mg₂SiO₄. Nature347, 655-658.) and of a melt with CI chondritic proportions of the major elements (Wang J., Davis A. M., Clayton R. N., Mayeda T. K., and Hashimoto A. (2001) Chemical and isotopic fractionation during the evaporation of the FeO-MgO-SiO₂-CaO-Al₂O₃-TiO₂-REE melt system. Geochim. Cosmochim. Acta65, 479-494.). There appears to be some compositional control on α_Si, whereas no compositional effects have been reported for α_Mg. We use the values of α_Si and α_Mg, to calculate the chemical compositions of the unevaporated precursors of a number of isotopically fractionated CAIs from CV chondrites whose chemical compositions and magnesium and silicon isotopic compositions have been previously measured.     

Nematode community structure in relation to metals in the southern of Caspian Sea

Spatial distribution and structure of nematode assemblages in coastal sediments of the southern part of the Caspian Sea were studied in relation to environmental factors. By considering metals, organic matter, Shannon diversity index(H), maturity index(MI) and trophic diversity(ITD), ecological quality status of sediment was also determined. Fifteen nematode species belonging to eleven genera were identified at the sampling sites. Average density of nematode inhabiting in sediment of the studied area was 139.78±98.91(ind. per 15.20 cm~2). According to redundancy analysis(RDA), there was high correlation between metals and some species. Based on biological indicators, the studied area had different environmental quality. Generally, chemical and biological indices showed different results while biological indices displayed similar results in more sites.     

Zur Auswertung astronomischer Aufnahmen mit dem automatischen Flächenphotometer

By measuring astronomical plates point by point by a microdensitometer information of very high redundancy is provided together with considerable noise due to the grains of the emulsion. In order to get astronomically relevant parameters the signal has to be separated from this noise and the data should be compressed. A chain of processing steps is described and analysed the crucial part of which being a variable twodimensional filter. This filter fits automatically its own band width to the incoming signal and reduces the number of data considerably (up to a factor of about 100). It is based on a modified HAAR transform and can be implemented easily on a relatively small processor working on line with the microdensitometer. The optimal separation of the noise is accomplished by a further variable digital filter (twodimensional KALMAN filter performed on an universal computer) the band width of which is also steered by the HAAR filter. The stars and galaxies in a larger field of the plate are picked up in the domain of the HAAR transform. Finally, the astronomically relevant parameters (coordinates and brightness of stars; furthermore diameter, axial ratio, position angle, perturbation, bright core et al. for galaxies) are obtained from the expansion of the intensity distribution into potential moments. The method is applicable e.g. to the determination of the brightness or colour distribution in a single galaxy or to the photometry of all stars and galaxies in a large part of the plate. The star photometry is obtained by integrating the intensity distribution of each object, if the characteristic curve of the plate is known from a calibration wedge copied onto the plate. Then no photoelectric sequency across the whole brightness range under consideration is needed besides of the zero point of the magnitude scale.     

Evolution effects in the distribution of distant galaxies?

The amplitudes of the two-point correlation function for galaxies are compared for galaxy catalogues extending to different depths. Strong evolution effects in the pattern of galaxy distribution seem to be present suggesting a secular increase of the clustering amplitude. Other explanations would involve large errors in the identification of faint objects as galaxies or a considerable contamination of the counts by very young highly redshifted galaxies as recently proposed by TINSLEY .     

Optical identifications of radio sources in the 5C areas

Results from optical identifications in the areas 5C1, 5C2, and 5C3 are summarized and compared. The identification rate is the same in all three areas within the statistical and systematic accuracy. No red quasars seem to exist; there may be a possible new group of bright starlike identifications. Galaxies deviate appreciably from their radio barycenter while quasars do not.     

Luminosity Profiles of 6 Dwarf Galaxies in the M 81/82 Group

Für 6 Zwerggalaxien sehr geringer Flächenhelligkeit aus der M81-Gruppe werden die wichtigsten photometrischen Parameter ermittelt. Zum ersten Mal werden Helligkeitsprofile extremer Zwerggalaxien außerhalb der lokalen Gruppe angegeben. Die Profile werden sehr viel besser durch ein Exponentialgesetz als durch das r1/4-Gesetz wiedergegeben. Zwischen irregulären und sphärischen Zwerggalaxien konnten keine signifikanten Unterschiede im Profil gefunden werden.