Orbital and thermal evolutions of four potential targets for a sample return space mission to a primitive near-Earth asteroid     

Patrick Michel  Marco Delbo 《Icarus》2010,209(2):520-534

In this paper, we present our study of the orbital and thermal evolutions, due to solar radiative heating, of four near-Earth asteroids (NEAs) considered as potential target candidates for sample return space missions to primitive asteroids. We used a dynamical model of the NEA population to estimate the most likely source region and orbital history of these objects. Then, for each asteroid, we integrated numerically over their entire lifetime a set of 14 initially indistinguishable orbit (clones), obtained by small variations of the nominal initial conditions. Using a thermal model, we then computed surface and sub-surface temperatures of these bodies during their dynamical history. Our aim is to determine whether these bodies are likely to have experienced high temperature level, and whether great temperature changes can be expected due to the orbital changes as well as their maximum and minimum values. Such information is important in the framework of sample return space missions whose goal is to bring back pristine materials. The knowledge of the temperature range of materials at different depth over the orbital evolution of potential targets can help defining sampling strategies that ensure the likelihood that unaltered material will be brought back. Our results suggest that for all the considered potential targets, the surface has experienced for some time temperatures greater than 400 K and at most 500 K with 50% probability. This probability drops rapidly with increasing temperature. Sub-surface materials at a depth of only 3 cm are much more protected from high temperature and generally do not reach temperatures exceeding 450 K (with 50% probability). They should thus be unaltered at this depth at least from a Sun-driven heating point of view. On the other hand, surface material for some of the considered objects can have a range of temperature which can make them less reliable as pristine materials. However, it is assumed here that the same material is constantly exposed to solar heat, while regolith turnover may occur. The latter can be caused by different processes such as seismic shaking and/or impact cratering. This would reduce the total time that materials are exposed to a certain temperature. Thus, it is very likely that a sample collected from any of the four considered targets, or any primitive NEA with similar dynamical properties, will have components that will be thermally unaltered as long as some of it comes from only 3 to 5 cm depth. Such a depth is not considered difficult to reach with some of the current designs of sampling devices.  相似文献   

Experimental Validation of Modified Barton’s Model for Rock Fractures   总被引：2，自引：2，他引：0  

Pooyan Asadollahi  Marco C. A. Invernizzi  Simone Addotto  Fulvio Tonon 《Rock Mechanics and Rock Engineering》2010,43(5):597-613

Among the constitutive models for rock fractures developed over the years, Barton’s empirical model has been widely used. Although Barton’s failure criterion predicts peak shear strength of rock fractures with acceptable precision, it has some limitations in estimating the peak shear displacement, post-peak shear strength, dilation, and surface degradation. The first author modified Barton’s original model in order to address these limitations. In this study, the modified Barton’s model (the peak shear displacement, the shear stress–displacement curve, and the dilation displacement) is validated by conducting a series of direct shear tests.  相似文献   

Sardignaite, a new mineral, the second known bismuth molybdate: description and crystal structure     

Paolo Orlandi  Marco Pasero  Simona Bigi 《Mineralogy and Petrology》2010,100(1-2):17-22

The new mineral sardignaite, a bismuth molybdate with formula BiMo₂O₇(OH)·2H₂O, occurs in quartz veins within a granitic rock at Su Senargiu, near Sarroch, Sardegna, Italy. The name is after the locality. Sardignaite occurs a thin prismatic crystals up to 1 mm in length, with pale yellow color and a white streak. It is transparent with adamantine lustre, non fluorescent, and brittle with a conchoidal fracture. It is associated with bismuthinite, bismoclite, molybdenite, ferrimolybdite, koechlinite, wulfenite, and the new mineral IMA 2009–022. Mohs hardness is ca. 3. D _calc is 4.82 g/cm³. The mineral is monoclinic, space group P2₁/m, with a 5.7797(7), b 11.567(1), c 6.3344(8) Å, β 113.360(9)°, V 388.8(1) ų. The strongest lines in the powder X-ray diffraction pattern are d(I)(hkl): 3.206(100)(031), 5.03(80)(?101), 1.992(45)(221), 3.120(32)(130). The crystal structure of sardignaite was solved to R(F) 0.056 using single-crystal X-ray diffraction data, and is characterized by edge-sharing dimers of [MoO₅(H₂O)] octahedra, linked to each other through corner-sharing to give rise to corrugated columns running along b. Such columns are held together by Bi³⁺ cations, eight-fold coordinated by 7 O + 1 (OH). Both the mineral and its name were approved by the IMA-CNMNC.  相似文献   

Quantitative vulnerability estimation for scenario-based landslide hazards   总被引：4，自引：1，他引：3  

Zhihong Li  Farrokh Nadim  Hongwei Huang  Marco Uzielli  Suzanne Lacasse 《Landslides》2010,7(2):125-134

Within the engineering profession and natural sciences, vulnerability is widely accepted to be defined as the degree of loss (or damage) to a given element or set of elements within the area affected by a threat. The value of vulnerability is expressed nondimensionally between 0 and 1. It is a fundamental component in the evaluation of landslide risk, and its accurate estimation is essential in making a reasonable prediction of the landslide consequences. Obviously, vulnerability to landslides depends not only on the characteristics of the element(s) at risk but also on the landslide intensity. This paper summarizes previous research on vulnerability to landslides and proposes a new quantitative model for vulnerability of structures and persons based on landslide intensity and resistance of exposed elements. In addition, an approximate function is suggested for estimating the vulnerability of persons in structures. Different methods for estimating the vulnerability of various elements to slow or rapid landslides are discussed. Finally, the application of the new model is illustrated through an example.  相似文献   

The catalog of the meteorite collection of the Italian Museum of Planetary Sciences in Prato (Italy)     

Marco Morelli  Annarita Franza  Daniela Faggi  Giovanni Pratesi 《Meteoritics & planetary science》2023,58(7):945-954

For the first time, this paper presents to the planetary scientists' community the catalog of the meteorite collection preserved at the Italian Museum of Planetary Sciences (Museo Italiano di Scienze Planetarie, henceforth MISP) in Prato (Italy). Founded in 2005, MISP is a type specimen official repository approved by the Nomenclature Committee of the Meteoritical Society. It represents one of the few museums worldwide entirely devoted to planetary sciences. The catalog of its meteorite collection encompasses 430 meteorites for a total of 1536 specimens, including 291 thin sections, 184 thick sections, and 278 specimens that MISP has classified. Furthermore, MISP is currently classifying 57 other meteorites. Some samples were found during meteorite recovery expeditions in hot deserts, promoted by MISP in collaboration with diverse Italian universities and national research institutions. MISP also keeps an impact rocks collection comprising 257 samples. In a country like Italy, where most of the collected meteorites are housed in museums whose catalogs are not available online, the publication of the MISP meteorite collection catalog, together with the catalog of the impact rocks collection, represents not only a significant scientific primary source but also a remarkable tool for disseminating meteoritics to nonresearch audiences in educational activities and citizen science projects.  相似文献   

Using DORIS measurements for modeling the vertical total electron content of the Earth’s ionosphere     

Denise Dettmering  Marco Limberger  Michael Schmidt 《Journal of Geodesy》2014,88(12):1131-1143

The Doppler orbitography and radiopositioning integrated by satellite (DORIS) system was originally developed for precise orbit determination of low Earth orbiting (LEO) satellites. Beyond that, it is highly qualified for modeling the distribution of electrons within the Earth’s ionosphere. It measures with two frequencies in L-band with a relative frequency ratio close to 5. Since the terrestrial ground beacons are distributed quite homogeneously and several LEOs are equipped with modern receivers, a good applicability for global vertical total electron content (VTEC) modeling can be expected. This paper investigates the capability of DORIS dual-frequency phase observations for deriving VTEC and the contribution of these data to global VTEC modeling. The DORIS preprocessing is performed similar to commonly used global navigation satellite systems (GNSS) preprocessing. However, the absolute DORIS VTEC level is taken from global ionospheric maps (GIM) provided by the International GNSS Service (IGS) as the DORIS data contain no absolute information. DORIS-derived VTEC values show good consistency with IGS GIMs with a RMS between 2 and 3 total electron content units (TECU) depending on solar activity which can be reduced to less than 2 TECU when using only observations with elevation angles higher than \(50^\circ \) . The combination of DORIS VTEC with data from other space-geodetic measurement techniques improves the accuracy of global VTEC models significantly. If DORIS VTEC data is used to update IGS GIMs, an improvement of up to 12  % can be achieved. The accuracy directly beneath the DORIS satellites’ ground-tracks ranges between 1.5 and 3.5 TECU assuming a precision of 2.5 TECU for altimeter-derived VTEC values which have been used for validation purposes.  相似文献   

Mechanisms of failure on terraced slopes: the Valtellina case (northern Italy)   总被引：1，自引：1，他引：0  

Corrado A. S. Camera  Tiziana Apuani  Marco Masetti 《Landslides》2014,11(1):43-54

Slopes that are terraced by means of dry-stone retaining walls are very common in the alpine environment. In Valtellina, a typical Italian alpine valley, these slopes are widespread and quite often involved in superficial mass movements that can result in severe damage and casualties. For an in-depth understanding of the processes that can trigger these events, numerical modeling of groundwater movement and a related stability analysis were performed on a detailed scale, based on an intensive monitoring of rainfall events and groundwater movement. Field observations suggest that the formation of a perched groundwater table at the contact between the bedrock and the backfill soil of walls as well as the concomitant saturation of this backfill soil are the determining factors of potential slope failure. The numerical models support these observations. In addition, the models are able to explain the mechanisms of formation of perched water tables, highlighting the factors that can influence groundwater levels and slope instabilities.  相似文献   

Human alteration of groundwater–surface water interactions (Sagittario River,Central Italy): implication for flow regime,contaminant fate and invertebrate response     

Mariachiara Caschetto  Maurizio Barbieri  Diana M. P. Galassi  Lucia Mastrorillo  Sergio Rusi  Fabio Stoch  Alessia Di Cioccio  Marco Petitta 《Environmental Earth Sciences》2014,71(4):1791-1807

Many rivers worldwide are undergoing severe man-induced alterations which are reflected also in changes of the degree of connectivity between surface waters and groundwater. Pollution, irrigation withdrawal, alteration of freshwater flows, road construction, surface water diversion, soil erosion in agriculture, deforestation and dam building have led to some irreversible species losses and severe changes in community composition of freshwater ecosystems. Taking into account the impact of damming and flow diversion on natural river discharge, the present study is aimed at (i) evaluating the effects of anthropogenic changes on groundwater/surface water interactions; (ii) analyzing the fate of nitrogenous pollutants at the floodplain scale; and (iii) describing the overall response of invertebrate assemblages to such changes. Hydrogeological, geochemical and isotopic data revealed short- and long-term changes in hydrology, allowing the assessment of the hydrogeological setting and the evaluation of potential contamination by nitrogen compounds. Water isotopes allowed distinguishing a shallow aquifer locally fed by zenithal recharge and river losses, and a deeper aquifer/aquitard system fed by surrounding carbonate aquifers. This system was found to retain ammonium and, through the shallow aquifer, release it in surface running waters via the hyporheic zone of the riverbed. All these factors influence river ecosystem health. As many environmental drivers entered in action offering a multiple-component artificial environment, a clear relationship between river flow alteration and benthic and hyporheic invertebrate diversity was not found, being species response driven by the combination of three main stressors: ammonium pollution, man-induced changes in river morphology and altered discharge regime.  相似文献   

Monitoring large oil slick dynamics with moderate resolution multispectral satellite data     

Pieralberto Maianti  Marco Rusmini  Riccardo Tortini  Giorgio Dalla Via  Federico Frassy  Andrea Marchesi  Francesco Rota Nodari  Marco Gianinetto 《Natural Hazards》2014,73(2):473-492

Accidental release of crude oil into the sea due to human activity causes water pollution and heavy damages to natural ecosystems killing birds, fish, mammals and other organisms. A number of monitoring systems are used for tracking the spills and their effects on the marine environment, as well as for collecting data for feeding models. Among them, Earth observation technologies play a crucial role and moderate spatial resolution satellite systems are able to collect images with a very short revisit time or even daily. This paper describes the use of Moderate-Resolution Imaging Spectroradiometer data for monitoring large oil slicks with the fluorescence/emissivity index and object-based image analysis. Two case studies are presented: the Deepwater Horizon (2010) and the Campos Basin (2011) oil spill accidents. Results show that it is possible to track the dynamics of the slick both for massive and long-lasting accidents and for smaller and very quick accidents. The main advantages of the method proposed are a straightforward implementation, a fast and semi-automated data processing and the capability of integration of daytime and nighttime acquisitions, as well as its adaptability to different sensors.  相似文献   

LightSquared effects on estimated C/N 0, pseudoranges and positions     

Marco Rao  Cillian O’Driscoll  Daniele Borio  Joaquim Fortuny 《GPS Solutions》2014,18(1):1-13

We present experimental results showing the impact of the proposed LightSquared (LS) Long-term Evolution (LTE) signals on both GPS and Galileo civil modulations in the L1/E1 band. The experiments were conducted in radiated mode in a large anechoic chamber. Three Galileo enabled receivers were chosen for the tests, and a state of the art GNSS signal generator was used to simulate both GPS and Galileo signals. The LTE signals were generated by an Agilent Programmable Signal Generator with a license to generate the signals according to the 3GPP LTE FDD standard. The interference impact was measured in terms of a Carrier-to-Noise power spectral density ratio (C/N ₀) degradation, in accordance with the methodology which the LS/GPS Technical Working Group (TWG) established by mandate of the FCC. A model for determining the impact of the LS signal on the considered GNSS signals is provided and is validated against experimental data. It is shown that the Galileo E1 Open Service (OS) signal is marginally more susceptible to this form of interference than the GPS L1 C/A signal due to its greater proximity to the lower edge of the L1 band. The impact of LS interference was further analyzed in terms of pseudorange and position errors. Despite its relevance for most GNSS users, this aspect was not considered by the TWG. Measurement and position domain analysis along with the study of the LS impact on the Galileo OS signals are the major contributions. The analysis confirms the results obtained by the TWG and shows that the receiver front-end plays a major role in protecting GNSS signals against RF interference. While it appears that, for now, the LS network will not be deployed, the approach taken and the results obtained herein can be readily adapted for any future terrestrial mobile network that may take the place of LS.  相似文献