Geologic constraints on the origin of red organic‐rich material on Ceres          下载免费PDF全文

C. M. Pieters  A. Nathues  G. Thangjam  M. Hoffmann  T. Platz  M. C. de Sanctis  E. Ammannito  F. Tosi  F. Zambon  J. H. Pasckert  H. Hiesinger  S. E. Schröder  R. Jaumann  K.‐D. Matz  J. C. Castillo‐Rogez  O. Ruesch  L. A. McFadden  D. P. O'Brien  M. Sykes  C. A. Raymond  C. T. Russell 《Meteoritics & planetary science》2018,53(9):1983-1998

The geologic context of red organic‐rich materials (ROR) found across an elongated 200 km region on Ceres is evaluated with spectral information from the multispectral framing camera (FC) and the visible and near‐infrared mapping spectrometer (VIR) of Dawn. Discrete areas of ROR materials are found to be associated with small fresh craters less than a few hundred meters in diameter. Regions with the highest concentration of discrete ROR areas exhibit a weaker diffuse background of ROR materials. The observed pattern could be consistent with a field of secondary impacts, but no appropriate primary crater has been found. Both endogenic and exogenic sources are being considered for these distinctive organic materials.  相似文献   

An ordered probit model for seismic intensity data     

Michela?CamelettiEmail author  Valerio?De Rubeis  Clarissa?Ferrari  Paola?Sbarra  Patrizia?Tosi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(7):1593-1602

Seismic intensity, measured through the Mercalli–Cancani–Sieberg (MCS) scale, provides an assessment of ground shaking level deduced from building damages, any natural environment changes and from any observed effects or feelings. Generally, moving away from the earthquake epicentre, the effects are lower but intensities may vary in space, as there could be areas that amplify or reduce the shaking depending on the earthquake source geometry, geological features and local factors. Currently, the Istituto Nazionale di Geofisica e Vulcanologia analyzes, for each seismic event, intensity data collected through the online macroseismic questionnaire available at the web-page www.haisentitoilterremoto.it. Questionnaire responses are aggregated at the municipality level and analyzed to obtain an intensity defined on an ordinal categorical scale. The main aim of this work is to model macroseismic attenuation and obtain an intensity prediction equation which describes the decay of macroseismic intensity as a function of the magnitude and distance from the hypocentre. To do this we employ an ordered probit model, assuming that the intensity response variable is related through the link probit function to some predictors. Differently from what it is commonly done in the macroseismic literature, this approach takes properly into account the qualitative and ordinal nature of the macroseismic intensity as defined on the MCS scale. Using Markov chain Monte Carlo methods, we estimate the posterior probability of the intensity at each site. Moreover, by comparing observed and estimated intensities we are able to detect anomalous areas in terms of residuals. This kind of information can be useful for a better assessment of seismic risk and for promoting effective policies to reduce major damages.  相似文献   

Juno’s Earth flyby: the Jovian infrared Auroral Mapper preliminary results     

A. Adriani  M. L. Moriconi  A. Mura  F. Tosi  G. Sindoni  R. Noschese  A. Cicchetti  G. Filacchione 《Astrophysics and Space Science》2016,361(8):272

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Understanding dwarf galaxies as galactic building blocks     

Monica Tosi 《Astrophysics and Space Science》2003,284(2):651-660

This is a summary of a general discussion held during the third EuroConference on galaxy evolution. Various observational features of the stellar populations in present-day dwarf galaxies were presented to introduce the discussion on the possibility that these systems be the main building blocks of spiral and elliptical galaxies. Many people in the audience turned out to think that the inconsistencies among the observed properties of large and dwarf galaxies are too many to believe that the former are built up only by means of successive accretions of the latter. However, theorists of hierarchical galaxy formation suggested that present-day dwarfs are not representative of the galactic building blocks, which may be completely invisible nowadays. Some of them suggested that, contrary to what is usually assumed in hierarchical modelling, the actual building blocks were still fully gaseous systems when their major mergers occurred. If this is the case, then most of the inconsistencies can be overcome, and the scenario of hierarchical galaxy formation becomes not too different from that of a slow gas accretion. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Is I ZW 18 Really a Young Galaxy?     

A. Aloisi  M. Tosi  L. Greggio 《Astrophysics and Space Science》2001,276(2-4):421-428

To understand the role of dwarfs in the context of galaxy formation and evolution, we are studying the star-formation history of some representative irregular and blue compact dwarf galaxies by comparing the observed colour–magnitude diagrams with synthetic ones based on homogeneous sets of stellar evolutionary tracks. Here we present the results obtained for the blue compact I Zw 18, the most metal-poor galaxy known. Our simulations suggest star-formation activity started around 1–0.3 Gyr ago, with evidence of an intense burst around 15–20 Myr ago. I Zw 18 has turned out not to be a young object as previously suggested. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A tropical haze band in Titan’s stratosphere     

R. de Kok  P.G.J. Irwin  S. Vinatier  F. Tosi  S. Osprey  M.L. Moriconi 《Icarus》2010,207(1):485-490

Inspection of near-infrared images from Cassini’s Imaging Science Subsystem and Visual and Infrared Mapping Spectrometer have revealed a new feature in Titan’s haze structure: a narrow band of increased scattering by haze south of the equator. The band seems to indicate a region of very limited mixing in the lower stratosphere, which causes haze particles to be trapped there. This could explain the sharp separation between the two hemispheres, known as the north-south asymmetry, seen in images. The separation of the two hemispheres can also be seen in the stratosphere above 150 km using infrared spectra measured by Cassini’s Composite Infrared Spectrometer. Titan’s behaviour in the lower tropical stratosphere is remarkably similar to that of the Earth’s tropical stratosphere, which hints at possible common dynamical processes.  相似文献   

Saturn’s icy satellites investigated by Cassini-VIMS: II. Results at the end of nominal mission     

G. Filacchione  F. Capaccioni  J.N. Cuzzi  A. Coradini  P.D. Nicholson  R.H. Brown  F. Tosi  R. Jaumann 《Icarus》2010,206(2):507-523

We report the detailed analysis of the spectrophotometric properties of Saturn’s icy satellites as derived by full-disk observations obtained by visual and infrared mapping spectrometer (VIMS) experiment aboard Cassini. In this paper, we have extended the coverage until the end of the Cassini’s nominal mission (June 1st 2008), while a previous paper (Filacchione, G., and 28 colleagues [2007]. Icarus 186, 259-290, hereby referred to as Paper I) reported the preliminary results of this study.During the four years of nominal mission, VIMS has observed the entire population of Saturn’s icy satellites allowing us to make a comparative analysis of the VIS-NIR spectral properties of the major satellites (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus) and irregular moons (Atlas, Prometheus, Pandora, Janus, Epimetheus, Telesto, Calypso, Phoebe). The results we discuss here are derived from the entire dataset available at June 2008 which consists of 1417 full-disk observations acquired from a variety of distances and inclinations from the equatorial plane, with different phase angles and hemispheric coverage. The most important spectrophotometric indicators (as defined in Paper I: I/F continua at 0.55 μm, 1.822 μm and 3.547 μm, visible spectral slopes, water and carbon dioxide bands depths and positions) are calculated for each observation in order to investigate the disk-integrated composition of the satellites, the distribution of water ice respect to “contaminants” abundances and typical regolith grain properties. These quantities vary from the almost pure water ice surfaces of Enceladus and Calypso to the organic and carbon dioxide rich Hyperion, Iapetus and Phoebe. Janus visible colors are intermediate between these two classes having a slightly positive spectral slope. These results could help to decipher the origins and evolutionary history of the minor moons of the Saturn’s system. We introduce a polar representation of the spectrophotometric parameters as function of the solar phase angle (along radial distance) and of the effective longitude interval illuminated by the Sun and covered by VIMS during the observation (in azimuth) to better investigate the spatial distribution of the spectrophotometric quantities across the regular satellites hemispheres. Finally, we report the observed spectral positions of the 4.26 μm band of the carbon dioxide present in the surface material of three outermost moons Hyperion, Iapetus and Phoebe.  相似文献   

The contribution of marine geology to the knowledge of marine coastal environment off the Campania region (southern Italy): the geological map n. 502 “Agropoli” (southern Campania)     

Gemma Aiello  Ennio Marsella 《Marine Geophysical Researches》2013,34(2):89-113

The marine geological map n. 502 “Agropoli”, located offshore the Cilento Promontory, southern Italy, is here described and the regional geology interpreted, particularly referring to water depths between the 30 and 200 m isobaths. The geologic map has been constructed in the frame of a research program financed by the National Geological Survey of Italy (CARG Project), finalized to the construction of up-to-date cartography of the Campania region. Geological and geophysical data on the continental shelf and slope offshore of the Southern Campania region have been collected in the study area, bounded northwards by the Salerno Gulf and southwards by the Policastro Gulf. A high resolution multibeam bathymetry allowed for the construction of a marine digital elevation map; sidescan sonar profiles also have been collected and interpreted. The latter, merged to the bathymetry, have represented the base for the marine geologic cartography. The integrated geologic interpretation of seismic, bathymetric and sidescan sonar data has been calibrated by sea-bottom samples. The morpho-structures and the seismic sequences overlying the outcrops of acoustic basement reported in the cartographic representation have been studied in detail using single-channel seismics. The interpretation of seismic profiles has been a support for the reconstruction of the stratigraphic and structural setting of the Quaternary continental shelf successions and the outcrops of rocky acoustic basement in correspondence to the Licosa Cape morpho-structural high. These areas result from the seaward prolongation of the stratigraphic and structural units, widely cropping out in the surrounding emerged sector of the Cilento Promontory. The cartographic approach is based on the recognition of laterally coeval depositional systems, interpreted in the frame of the system tracts of the Late Quaternary depositional sequence. We present evidence of now subaqueous terraces inferred to be palaeoshorelines representing past sea-level positions and tentatively correlated these to oxygen isotopic stratigraphy.  相似文献   

A new perspective on the irregular satellites of Saturn – II. Dynamical and physical origin     

D. Turrini  F. Marzari  F. Tosi 《Monthly notices of the Royal Astronomical Society》2009,392(1):455-474

The origin of the irregular satellites of the giant planets has been long debated since their discovery. Their dynamical features argue against an in situ formation suggesting that they are captured bodies, yet there is no global consensus on the physical process at the basis of their capture. In this paper, we explore the collisional capture scenario, where the actual satellites originated from impacts occurred within Saturn's influence sphere. By modelling the inverse capture problem, we estimated the families of orbits of the possible parent bodies and the specific impulse needed for their capture. The orbits of these putative parent bodies are compared to those of the minor bodies of the outer Solar system to outline their possible region of formation. Finally, we tested the collisional capture hypothesis on Phoebe by taking advantage of the data supplied by Cassini on its major crater, Jason. Our results presented a realistic range of solutions matching the observational and dynamical data.  相似文献   

Star formation in the Small Magellanic Cloud: the youngest star clusters     

E. Sabbi  A. Nota  J. S. Gallagher  M. Tosi  L. R. Carlson  M. Sirianni  M. Meixner  L. J. Smith  M. S. Oey  R. Walterbos  A. Pasquali  L. Angeretti 《Astrophysics and Space Science》2009,324(2-4):101-107

We combined optical Hubble Space Telescope ACS images with mid-infrared Spitzer data of the two young star clusters NGC346 and NGC602 in the Small Magellanic Cloud, to study how local and global conditions may affect the process of star formation. We found that, while general conditions such as metallicity, or the mass or morphological type of the parent galaxy do not strongly affect the process of star formation, local conditions such as the gas and stellar density can affect both how star formation occurs and propagates, and also the evolution of a star cluster from early times.  相似文献