On the stability of the satellites of asteroid 87 Sylvia

The triple asteroidal system (87) Sylvia is composed of a 280-km primary and two small moonlets named Romulus and Remus ( Marchis et al. 2005b ). Sylvia is located in the main asteroid belt, with semi-major axis of about 3.49 au, eccentricity of 0.08 and 11° of orbital inclination. The satellites are in nearly equatorial circular orbits around the primary, with orbital radius of about 1360 km (Romulus) and 710 km (Remus). In this work, we study the stability of the satellites Romulus and Remus. In order to identify the effects and the contribution of each perturber, we performed numerical simulations considering a set of different systems. The results from the three-body problem, Sylvia–Romulus–Remus, show no significant variation of their orbital elements. However, the inclinations of the satellites present a long-period evolution with amplitude of about 20° when the Sun is included in the system. Such amplitude is amplified to more than 50° when Jupiter is included. These evolutions are very similar for both satellites. An analysis of these results shows that Romulus and Remus are librating in a secular resonance and their longitude of the nodes are locked to each other. Further simulations show that the amplitude of oscillation of the satellites' inclination can reach higher values depending on the initial values of their longitude of pericentre. In those cases, the satellites get caught in an evection resonance with Jupiter, their eccentricities grow and they eventually collide with Sylvia. However, the orbital evolutions of the satellites became completely stable when the oblateness of Sylvia is included in the simulations. The value of Sylvia's J ₂ is about 0.17, which is very high. However, even just 0.1 per cent of this value is enough to keep the satellite's orbital elements with no significant variation.     

Element-Enrichment Factors in Lichens from Terceira, Santa Maria and Madeira Islands (Azores and Madeira Archipelagoes)

In this study, more than 20 minor and trace elements have been determined by INAA (instrumental neutron activation analysis), in different species of lichens in three Portuguese islands of the Central North Atlantic (Santa Maria, Terceira, and Madeira Islands). The foliose species Parmotrema bangii, Parmotrema robustum, Parmotrema crinitum, Flavoparmelia caperata, Platismatia glauca, and the fruiticose species Ramalina canariensis, Ramalina farinacea, Ramalina implectens, Ramalina pusilla, Cladonia furcata, Cladonia coniocraea, Usnea dasaea, Usnea esperantiana, were the collected species. Samples of superficial soils were also collected and the fraction below 64 m was analysed. The enrichment factors relative to this fraction using Al as the normalising element were calculated. Fruiticose and foliose lichens displayed different EF values concerning bromine and potassium. The first was more enriched in the foliose species while the latter was more enriched in the fruiticose species and was assigned to the physiological response. Enrichment was found for Mg, Cs, As, Hg, Na, Zn, and Cl, in all the species. Lichen-based concentration patterns were shown for Na, Al, Cl, Br, Sb, Ce, and Hg and compared to similar patterns in Portugal mainland. In general, the patterns compared well except for Cl, Na, and Br. Background levels of the epiphytic lichens collected in the islands were obtained.     

Geodynamic Technique Applied to the Volcanic Activity Forecast of Lanzarote Island in Spain

In accordance with the Agreement of Sino-Spain Science and Technology Cooperation,the Institute of Seismology,SSB of China and the Institute of Astronomy and Geodesy of Spain have together performed research at the Geodynamics Laboratory of Lanzarote(Canary Islands)with geodynamic instrumentation.Researchers conducted observation and then analyzed the data compiled.Researchers using the advanced geodynamic instruments could monitor the volcanic activity and seismicity in order to forecast the volcanic eruption and earthquakes.The results of this paper are obtained from this scientific and technological cooperation of the two institutes between China and Spain.     

Atacama Field Campaign: laboratory and in-situ measurements for remote sensing applications

This work presents the preliminary results of the first field calibration campaign performed in the Atacama Desert, Chile, between the 18 and 22 August 2014, called the Atacama Field Campaign (ATAFIC 2014). In situ measurements were performed in order to spectrally characterize the surface reflectance spectra between 0.3 and 2.5?µm, radiometric temperature (8.0–14.0?µm) and atmospheric measurements. A soil sample was collected and analyzed using Fourier Transform Infrared Spectroscopy and X-Ray Diffraction techniques to characterize the surface reflectance spectra and mineralogical composition, respectively. ASTER land surface emissivity in addition to GOES, MODIS and Landsat-8 land surface temperature (LST) were also used. Results showed that the spectral features of the Atacama soil and the characteristics of this geographical zone, which is featured as the most hyper-arid and cloudless place in the world, make this area a potential target for surface reflectance characterization. Day and night LST comparison between field and remote sensing data are lower than 2?K and the Root Mean Square Error for land surface emissivity is close to 2%. This work opens the possibilities to consider the Atacama Desert as a reference target for calibration and validation activities for earth observation missions’ purposes.     

Empirical relationships between macroseimic intensity and instrumental ground motion parameters for the intermediate-depth earthquakes of Vrancea region,Romania

Natural Hazards - Empirical relationships between MSK macroseismic intensity and several engineering ground motion parameters are developed using the macroseismic and instrumental data available...     

An epigenetic origin for the Passagem de Mariana gold deposit, Quadrilátero Ferrífero, Minas Gerais, Brazil

The gold–tourmaline quartz–vein deposit of Passagem de Mariana, in the southeastern part of the Quadrilátero Ferrífero, produced more than 60 tonne of gold, from the end of the 17th Century until 1954. The mine has not operated since 1985. Orebodies are veins composed of white quartz (> 60 vol.%), carbonate (ankerite), tourmaline, sericite and sulfides. Tourmaline (dravite), up to 10 vol.% of the vein, occurs as subhedral, coarse, commonly zoned crystals, and is concentrated along vein boundaries and on the edges of host rock inclusions in the veins. Tourmaline is present in all rock types in the mine, but the chemical composition of the host rocks determinates the intensity of tourmalinization, with the alteration being greater in sericitic phyllites, graphite–sericite phyllites, and calcareous rocks. The most abundant sulfide is arsenopyrite, which is normally associated with pyrite and pyrrhotite. Minor amounts of chalcopyrite, galena, löllingite, berthierite, and maldonite are present throughout the deposit. Sulfides are concentrated at veins boundary or are dispersed in the veins. Arsenopyrite is associated, most commonly, with calcareous rocks, and graphite–sericite phyllite. Pyrrhotite is usually found at the base of itabirites. Gold abundance is directly proportional to sulfide concentration. Hydrothermal alteration associated with the veins includes silicification, tourmalinization, and sulfidation. The mineralized zone is a shear zone associated with a bedding-parallel thrust fault that juxtaposes the itabirite (Lower Proterozoic Minas Supergroup) over other units. This shear zone/thrust fault extends for tens of km beyond the Passagem mine and hosts numerous gold deposits. The richest orebodies are along the itabirite footwall contact and within the graphite–sericite phyllite (Main orebody). Although many lithologic units were mineralized the graphite–sericite phyllite appears to have been most favorable for gold deposition.The area underwent three phases of deformation, D₁, D₂ and D₃. Mineral assemblages indicate upper-greenschist to lower-amphibolite conditions of regional metamorphism. Retrograde metamorphism, characterized by chloritization of biotite and chloritization and biotitization of garnet, developed locally. The gold-bearing veins crosscut the main foliation and lithologic contacts at low angle and occur within, or are in contact with, all lithotypes. Field and laboratory data indicate that gold mineralization at Passagem de Mariana is epigenetic. Gold deposition occurred after the peak of metamorphism, within the late- to post-D₂ period of deformation, which is correlated with second set of structures of Trasamazonian age of Alkmim and Marshak [Alkmim, F.F., Marshak, S., 1998. Transamazonian Orogeny in the Southern São Francisco Craton Region, Minas Gerais, Brazil: evidence for Paleoproterozoic collision and collapse in the Quadrilátero Ferrífero. Precambrian Research 90, 29-58.], indicating that the gold mineralization occurred between 2.124 and 2.04 Ga. We choose to regard Passagem de Marina as an orogenic gold deposit as defined by Groves et al. [Groves, D. I., Goldfarb, R.J., Gebre-Mariam, M., Hagemann, S.G., Robert, F., 1998. Orogenic gold deposits: A proposed classification in the context of their crustal distribution and relationship to other gold deposit types. Ore Geology Reviews 13, 7-27.], i.e., an epigenetic, structurally-hosted lode–gold vein system in a deformed metamorphic terrane.     

3-D electromagnetic imaging of a Palaeozoic plate-tectonic boundary segment in SW Iberian Variscides (S Alentejo, Portugal)

In SW Iberian Variscides, the boundary between the South Portuguese Zone (SPZ) and the Ossa Morena Zone (OMZ) corresponds to a major tectonic suture that includes the Beja Acebuches Ophiolite Complex (BAOC) and the Pulo do Lobo Antiform Terrane (PLAT). Three sub-parallel and approximately equidistant MT profiles were performed, covering a critical area of this Palaeozoic plate-tectonic boundary in Portugal; the profiles, running roughly along an NE–SW direction, are sub-perpendicular to the main Variscan tectonic features. Results of the three-dimensional (3-D) modelling of MT data allow to generate, for the first time, a 3-D electromagnetic imaging of the OMZ–SPZ boundary, which reveals different conductive and resistive domains that display morphological variations in depth and are intersected by two major sub-vertical corridors; these corridors coincide roughly with the NE–SW, Messejana strike–slip fault zone and with the WNW–ESE, Ferreira–Ficalho thrust fault zone. The distribution of the shallow resistive domains is consistent with the lithological and structural features observed and mapped, integrating the expected electrical features produced by igneous intrusions and metamorphic sequences of variable nature and age. The development in depth of these resistive domains suggests that: (1) a significant vertical displacement along an early tectonic structure, subsequently re-taken by the Messejana fault-zone in Late-Variscan times, has to be considered to explain differences in deepness of the base of the Precambrian–Cambrian metamorphic pile; (2) hidden, syn- to late-collision igneous bodies intrude the meta-sedimentary sequences of PLAT; (3) the roots of BAOC are inferred from 12 km depth onwards, forming a moderate resistive band located between two middle-crust conductive layers extended to the north (in OMZ) and to the south (in SPZ). These conductive layers overlap the Iberian Reflective Body (evidenced by the available seismic reflection data) and are interpreted as part of an important middle-crust décollement developed immediately above or coinciding with the top of a graphite-bearing granulitic basement.     

A Validation of MODIS Snowcover Products in Romania: Challenges and Future Directions

The MODIS snowcover product is one of many geophysical products derived from MODIS data. A cross‐validation of the MODIS snowcover daily products with data obtained from the meteorological network stations was conducted for the entire territory of Romania. The validation time interval covered the period between 29 October, 2004 and 1 May, 2005. The overall accuracy for the whole set of cloud‐free useful data proved to be 95%. The validation time interval included the three common snow situations: (1) late autumn months where 37.1% of the initial set of the data was used, and the overall accuracy was 98.6%; (2) the “winter” months where the clouds reduced the set of useful data – 31.75%– and the overall accuracy was 93.7%; and (3) the months of February and March which returned the highest accuracy (> 95%). Additionally, a cross‐validation using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) high‐resolution imagery was carried out. Furthermore, the MODIS, meteorological data and ASTER data were integrated into a Geographic Information System (GIS) environment to perform flexible and comprehensive cross‐checking followed by a thematic analysis based on additional sets of data such as digital elevation models (DEMs) and land‐cover datasets.