Fundamental physics and absolute positioning metrology with the MAGIA lunar orbiter

MAGIA is a mission approved by the Italian Space Agency (ASI) for Phase A study. Using a single large-diameter laser retroreflector, a large laser retroreflector array and an atomic clock onboard MAGIA we propose to perform several fundamental physics and absolute positioning metrology experiments: VESPUCCI, an improved test of the gravitational redshift in the Earth?CMoon system predicted by General Relativity; MoonLIGHT-P, a precursor test of a second generation Lunar Laser Ranging (LLR) payload for precision gravity and lunar science measurements under development for NASA, ASI and robotic missions of the proposed International Lunar Network (ILN); Selenocenter (the center of mass of the Moon), the determination of the position of the Moon center of mass with respect to the International Terrestrial Reference Frame/System (ITRF/ITRS); this will be compared to the one from Apollo and Lunokhod retroreflectors on the surface; MapRef, the absolute referencing of MAGIA??s lunar altimetry, gravity and geochemical maps with respect to the ITRF/ITRS. The absolute positioning of MAGIA will be achieved thanks to: (1) the laboratory characterization of the retroreflector performance at INFN-LNF; (2) the precision tracking by the International Laser Ranging Service (ILRS), which gives two fundamental contributions to the ITRF/ITRS, i.e. the metrological definition of the geocenter (the Earth center of mass) and of the scale of length; (3) the radio science and accelerometer payloads; (4) support by the ASI Space Geodesy Center in Matera, Italy. Future ILN geodetic nodes equipped with MoonLIGHT and the Apollo/Lunokhod retroreflectors will become the first realization of the International Moon Reference Frame (IMRF), the lunar analog of the ITRF.     

Petrographic and geochemical characterization of the granitic rocks of the Araguainha impact crater,Brazil

Petrographic and geochemical data obtained on the Araguainha impact crater (Goiás/Mato Grosso States, Brazil) indicate the existence of several molten products that originated during impact‐induced congruent melting of an alkali‐granite exposed in the inner part of the central uplift of the structure. Although previous studies have described these melts to some extent, there is no detailed discussion on the petrographic and geochemical variability in the granite and its impactogenic derivatives, and therefore, little is known about the geochemical behavior and mobility of trace elements during its fusion in the central part of the Araguainha crater. This paper demonstrates that the preserved granitoid exposed in the core of the structure is a magnesium‐rich granite, similar to postcollisional, A‐type granites, also found in terrains outside the Araguainha crater, in the Brasília orogenic belt. The molten products are texturally distinct and different from the original rock, but have very similar geochemical composition, making it difficult to separate these lithotypes based on concentrations of major and minor elements. This also applies for trace and rare earth elements (REE), thus indicating a high degree of homogenization during impact‐induced congruent melting under high pressure and postshock temperature conditions. Petrographic observations, along with geochemical data, indicate that melting occurs selectively, where some of the elements are transported with the melt. Simultaneously, there is an effective dissolution of the rock (granite), which leads to entrainment of the most resistant solid phases (intact or partially molten minerals) into the melt. Minerals more resistant to melting, such as quartz and oxides, contribute substantially to a chemical balance between the preserved granite and the fusion products generated during the meteoritic impact.     

The meteoritic origin of Tutankhamun's iron dagger blade

Scholars have long discussed the introduction and spread of iron metallurgy in different civilizations. The sporadic use of iron has been reported in the Eastern Mediterranean area from the late Neolithic period to the Bronze Age. Despite the rare existence of smelted iron, it is generally assumed that early iron objects were produced from meteoritic iron. Nevertheless, the methods of working the metal, its use, and diffusion are contentious issues compromised by lack of detailed analysis. Since its discovery in 1925, the meteoritic origin of the iron dagger blade from the sarcophagus of the ancient Egyptian King Tutankhamun (14th C. BCE) has been the subject of debate and previous analyses yielded controversial results. We show that the composition of the blade (Fe plus 10.8 wt% Ni and 0.58 wt% Co), accurately determined through portable x‐ray fluorescence spectrometry, strongly supports its meteoritic origin. In agreement with recent results of metallographic analysis of ancient iron artifacts from Gerzeh, our study confirms that ancient Egyptians attributed great value to meteoritic iron for the production of precious objects. Moreover, the high manufacturing quality of Tutankhamun's dagger blade, in comparison with other simple‐shaped meteoritic iron artifacts, suggests a significant mastery of ironworking in Tutankhamun's time.     

The 2dF Galaxy Redshift Survey: luminosity dependence of galaxy clustering

We investigate the dependence of the strength of galaxy clustering on intrinsic luminosity using the Anglo-Australian two degree field galaxy redshift survey (2dFGRS). The 2dFGRS is over an order of magnitude larger than previous redshift surveys used to address this issue. We measure the projected two-point correlation function of galaxies in a series of volume-limited samples. The projected correlation function is free from any distortion of the clustering pattern induced by peculiar motions and is well described by a power law in pair separation over the range     . The clustering of     galaxies in real space is well-fitted by a correlation length     and power-law slope     . The clustering amplitude increases slowly with absolute magnitude for galaxies fainter than M *, but rises more strongly at higher luminosities. At low luminosities, our results agree with measurements from the Southern Sky Redshift Survey 2 by Benoist et al. However, we find a weaker dependence of clustering strength on luminosity at the highest luminosities. The correlation function amplitude increases by a factor of 4.0 between     and −22.5, and the most luminous galaxies are 3.0 times more strongly clustered than L * galaxies. The power-law slope of the correlation function shows remarkably little variation for samples spanning a factor of 20 in luminosity. Our measurements are in very good agreement with the predictions of the hierarchical galaxy formation models of Benson et al.     

Study of a rockfall in a limy conglomerate canyon (Covarrubias, Burgos, N. Spain)

In this paper, a rockfall of some tenths of cubic metres of rock, occurred in a conglomerate canyon in the northern Castilian plateau (N-Central Spain), is described in detail. This includes the basic data (geology, mapping, meteorological data and rock involved), the mechanical mechanism of the instability, the propagation and reach of the fallen rock boulders and the final location of the pieces. The study is based on detailed geological, aerial photography and geotechnical studies and advance topographical measurements. Geological engineering techniques are used to analyze the instability initiation and rockfall propagation. This study contributes to a better understanding of the geological processes leading to the occurrence of calcareous canyons and cliffs in the drainage network of the upper Castilian plateau. It is also helpful to improve our knowledge on natural rockfall phenomena for risk engineering purposes aiming to quantify, control and mitigate associated hazards.     

Passive seismic control of cable-stayed bridges with damped resonant appendages

A study is conducted to investigate the effectiveness of attaching to cable-stayed bridges resonant appendages with a relatively small mass and a high damping ratio as a means to reduce their response to earthquake excitations. The study is based on a previously developed formulation that shows that the use of these appendages may increase the inherent damping of building structures and, as a result, may reduce their response to seismic disturbances. It includes numerical and experimental tests that are conducted to assess the validity of such a formulation for the case of cable-stayed bridges and the extent to which such appendages can reduce their seismic response. In the numerical study, an actual cable-stayed bridge is modelled with finite elements and analysed with and without the proposed appendages under different earthquake ground motions. Appendages with damping ratios of 10, 15, 20 and 30 per cent and masses that, respectively, represent 0.67, 1.5, 2.7 and 6.0 per cent of the total mass of the bridge are considered. In the experimental test, a 3.7 m long cable-stayed bridge and an appendage consisting of a small mass, a small spring and a small viscous damper are built and the bridge tested, without and with the appendage, on a pair of shaking tables which are set to reproduce ground acceleration records from past earthquakes. The damping ratio of the appendage in this test is 32 per cent and its mass represents about 8 per cent of the total mass of the bridge model. In the numerical test, it is found that the appendages reduce the longitudinal response of the bridge deck up to 88 per cent. Similarly, in the experimental test it is found that the appendage reduces the longitudinal bridge deck response by about 41 per cent. From these studies, it is concluded that the suggested appendages may indeed be effective in reducing the seismic response of cable-stayed bridges as they are for building structures.     

Travel-time residuals and three-dimensional velocity structure of Italy

Jeffreys-Bullen P and PKP travel-time residuals observed at more than 50 seismic stations distributed along Italy and surrounding areas in the time interval 1962–1979, indicate the complex velocity pattern of this region. Strong lateral velocity inhomogeneities and low velocity zones are required to explain the observed pattern of residuals. In particular, late arrivals of about 1 sec are observed in the Apenninic mountain range, requiring both greater crustal thickness and low velocity layers, coherent with seismic refraction data and surface wave dispersion measurements. The seismic stations located in the Western and Eastern Alps indicate the presence of high velocities. In the Western Alps the strong azimuthal variation of residuals and the high values of early arrivals have a close relationship to the Ivrea body, an intrusive crustal complex characterized by a velocity as high as 7–7.2 km/sec.A travel-time inversion performed with theAki et al. (1977) block model, confirms the peculiar characteristics and the sharp variations in the lithosphere of the whole Italian region, with values of velocity perturbations between many adjacent blocks, ranging in size from 50 to 100 km, and independent from the earth parametrization chosen, reaching values up to 10% in the lithospheric part and 5% in the asthenosphere. 3-D inversion requires also high velocity along the Tyrrhenian coastal margin, equivalent to an uprise of major crustal and lithospheric discontinuities along this part of the Italian peninsula. Moreover low velocity material must be present in the northern part of the Adriatic foreland, in the lithosphere-asthenosphere system, closely related to the stress and seismicity pattern, and the lateral bending of the lithosphere in the same region.