Aerosols scattering and near-infrared observations of the Martian surface

The presence of a scattered contribution in the atmosphere of Mars is a major problem for spectroscopic observations of the surface in the infrared since the main mineralogical absorptions have a typical depth of 1% and could be easily masked or subdued by atmospheric scattering. An estimate of the aerosol contribution between 0.77 and 2.6 microns was previously derived above Tharsis from ISM imaging spectroscopic data acquired from the Phobos 2 spacecraft in 1989. It is used here to investigate the effect of the scattering on the criteria that allow the mineralogical characterization of the surface

Composition of Syrtis Major volcanic plateau

Syrtis Major, a low-relief volcanic shield centered near 295 degrees 10 degrees N, is an old, well-preserved and exposed volcanic region on Mars which formed at the end of the heavy bombardment period. The composition of these volcanic materials has importance for understanding the thermal and chemical history of Mars. Imaging spectrometer data of the Syrtis Major volcanic plateau are used in this analysis to identify major compositional components. First and second order even channel reflectance spectra between 0.77 and 2.55 microns from four broad classes of materials on Syrtis Major are given. For the volcanic materials, there are three primary classes characterized by albedo, slope, and shape of the 10 micron band. To emphasize the latter, straight line continua were removed from each spectral segment and replotted in another figure. Each spectrum shows a band minima near 0.96 microns and 2.15 microns indicative of pyroxene mineral absorptions. Comparison of these band minima with studies of pyroxene reflectance spectra suggests that the pyroxenes in the volcanics of Syrtis Major are high calcium pyroxene with a Ca/(Mg+Fe+Ca) ratio of 0.2 to 0.3. The most likely pyroxene is an augite

The Relationship between State and Federal Tax Audits

In this paper we present an econometric analysis of state and federal tax audits. We first present results from a survey of state tax administrators. The survey results indicate that most state tax audit programs are small and rely extensively on information provided by the IRS, although some programs are large and sophisticated. We then present results from a detailed econometric analysis of Oregon state and federal tax returns and tax audits for tax year 1987. Our analysis generates three main conclusions. First, Oregon state and IRS selection criteria are similar, but not identical, suggesting that both tax agencies might benefit from greater sharing of information, especially in some audit classes. Second, Oregon state and IRS audit assessments are strongly positively correlated, as expected. Third, we estimate the shadow values associated with providing additional audit resources to the Oregon Department of Revenue and the IRS in various audit classes, and find that for the IRS the shadow values range from two to five dollars, while for Oregon the values range from one to three dollars.

Composition of weakly altered Martian crust

The mineralogic and chemical composition of weakly altered crust remains an unresolved question for Mars. Dark regions hold clues to the composition since they are thought to comprise surface exposures of weakly altered crustal materials. Understanding the in situ composition of relatively pristine crustal rocks in greater detail is important for investigating basic volcanic processes. Also, this will provide additional constraints on the chemical pathways by which pristine rocks are altered to produce the observed ferric iron-bearing assemblages and inferred clay silicate, sulphate, and magnetic oxide phases. Reflectance spectra of dark regions obtained with the ISM instrument are being used to determine the basic mineralogy of weakly altered crust for a variety of regions on Mars

Planetary Science Virtual Observatory architecture

In the framework of the Europlanet-RI program, a prototype of Virtual Observatory dedicated to Planetary Science was defined. Most of the activity was dedicated to the elaboration of standards to retrieve and visualize data in this field, and to provide light procedures to teams who wish to contribute with on-line data services. The architecture of this VO system and selected solutions are presented here, together with existing demonstrators

On discretization in time in simulations of particulate flows

We propose a time discretization scheme for a class of ordinary differential equations arising in simulations of fluid/particle flows. The scheme is intended to work robustly in the lubrication regime when the distance between two particles immersed in the fluid or between a particle and the wall tends to zero. The idea consists in introducing a small threshold for the particle-wall distance below which the real trajectory of the particle is replaced by an approximated one where the distance is kept equal to the threshold value. The error of this approximation is estimated both theoretically and by numerical experiments. Our time marching scheme can be easily incorporated into a full simulation method where the velocity of the fluid is obtained by a numerical solution to Stokes or Navier-Stokes equations. We also provide a derivation of the asymptotic expansion for the lubrication force (used in our numerical experiments) acting on a disk immersed in a Newtonian fluid and approaching the wall. The method of this derivation is new and can be easily adapted to other cases

The EPN-TAP protocol for the Planetary Science Virtual Observatory

A Data Access Protocol has been set up to search and retrieve Planetary Science data in general. This protocol will allow the user to select a subset of data from an archive in a standard way, based on the IVOA Table Access Protocol (TAP). The TAP mechanism is completed by an underlying Data Model and reference dictionaries. This paper describes the principle of the EPN- TAP protocol and interfaces, underlines the choices that have been made, and discusses possible evolutions.Comment: 21 pages. Submitted to Astronomy & Computing, S.I. Virtual Observator

Thermal maps and properties of comet 67P as derived from Rosetta/VIRTIS data

After a 10-year cruise, the Rosetta spacecraft began a close exploration of its main target, comet 67P/Churyumov-Gerasimenko, in July 2014. Since then, the Visible InfraRed Thermal Imaging Spectrometer (VIRTIS) acquired hyperspectral images of the comet’s surface with an unprecedented spatial resolution. VIRTIS data are routinely used to map the surface composition and to retrieve surface temperatures on the dayside of the comet. The thermal behavior of the surface of comet 67P is related to composition and physical properties that provide information about the nature and evolution of those materials. Here we present temperature maps of comet 67P that were observed by Rosetta under different illumination conditions and different local solar times