On the dynamics in the asteroids belt. Part II: Detailed study of the main resonances

The general theory exposed in the first part of this paper is applied to the following resonances with Jupiter's motion : 3/2, 2/1, 5/2, 3/1, 7/2, 4/1; these are the most relevant resonances for the asteroids. The whole analysis is performed in the framework of the spatial problem of three bodies, both in the circular and in the elliptic case. The results are also compared with the observed distribution of the asteroids.     

The role of syn-eruptive vesiculation on explosive basaltic activity at Mt. Etna,Italy

We investigated the dynamics of explosive activity at Mt. Etna between 31 August and 15 December 2006 by combining vesicle studies in the erupted products with measurements of the gas composition at the active, summit crater. The analysed scoria clasts present large, connected vesicles with complex shapes and smaller, isolated, spherical vesicles, the content of which increases in scoriae from the most explosive events. Gas geochemistry reports CO₂/SO₂ and SO₂/HCl ratios supporting a deep-derived gas phase for fire-fountain activity. By integrating results from scoria vesiculation and gas analysis we find that the highest energy episodes of Mt. Etna activity in 2006 were driven by a previously accumulated CO₂-rich gas phase but we highlight the lesser role of syn-eruptive vesicle nucleation driven by water exsolution during ascent. We conclude that syn-eruptive vesiculation is a common process in Etnean magmas that may promote a deeper conduit magma fragmentation and increase ash formation.     

Frontier Mountain 93001: A coarse‐grained,enstatite‐augite‐oligoclase‐rich,igneous rock from the acapulcoite‐lodranite parent asteroid

Abstract— The Frontier Mountain (FRO) 93001 meteorite is a 4.86 g fragment of an unshocked, medium‐ to coarse‐grained rock from the acapulcoite‐lodranite (AL) parent body. It consists of anhedral orthoenstatite (Fs_{13.3 ± 0.4}Wo_{3.1 ± 0.2}), augite (Fs_{6.1 ± 0.7}Wo_{42.3 ± 0.9}; Cr₂O₃ = 1.54 ± 0.03), and oligoclase (Ab_{80.5 ± 3.3}Or_{3.1 ± 0.6}) up to >1 cm in size enclosing polycrystalline aggregates of fine‐grained olivine (average grain size: 460 ± 210 μm) showing granoblastic textures, often associated with Fe,Ni metal, troilite, chromite (cr# = 0.91 ± 0.03; fe# = 0.62 ± 0.04), schreibersite, and phosphates. Such aggregates appear to have been corroded by a melt. They are interpreted as lodranitic xenoliths. After the igneous (the term “igneous” is used here strictly to describe rocks or minerals that solidified from molten material) lithology intruding an acapulcoite host in Lewis Cliff (LEW) 86220, FRO 93001 is the second‐known silicate‐rich melt from the AL parent asteroid. Despite some similarities, the silicate igneous component of FRO 93001 (i.e., the pyroxene‐plagioclase mineral assemblage) differs in being coarser‐grained and containing abundant enstatite. Melting‐crystallization modeling suggests that FRO 93001 formed through high‐degree partial melting (≥35 wt%; namely, ≥15 wt% silicate melting and ?20 wt% metal melting) of an acapulcoitic source rock, or its chondritic precursor, at temperatures ≥1200 °C, under reducing conditions. The resulting magnesium‐rich silicate melt then underwent equilibrium crystallization; prior to complete crystallization at ?1040 °C, it incorporated lodranitic xenoliths. FRO 93001 is the highest‐temperature melt from the AL parent‐body so far available in laboratory. The fact that FRO 93001 could form by partial melting and crystallization under equilibrium conditions, coupled with the lack of quench‐textures and evidence for shock deformation in the xenoliths, suggests that FRO 93001 is a magmatic rock produced by endogenic heating rather than impact melting.     

Geological constraints for earthquake faulting studies in the Colfiorito area (central Italy)

On September 26, 1997, at 00.33 h(GMT), a Mw 5.7 earthquake occurred in the axial zone of theUmbria-Marche Apennines of central Italy, in the Colfiorito basin area. At09.40 h (GMT), a M_w 6.0 earthquake again struck the area withinthe Colfiorito basin, a major intramontane basin filled with Quaternarycontinental deposits. The two main shocks, and the associated aftershockswere within a roughly NNW-SSE trending zone of largest damage (Imax10), in which ground deformation has been observed. Along this trend,Cello et al. (1997a) had mapped a few capable faults, showingtranstensional to pure extensional kinematics. Field inspection of themapped faults, carried out after the main shocks, revealed that some ofthem were locally reactivated (for lengths of several hundreds metres andsurface slip in the range of 2–8 cm) during the September 26, 1997earthquakes.     

Evidence for the role of the Atlantic multidecadal oscillation and the ocean heat uptake in hiatus prediction

The recent hiatus in global temperature at the surface has been analysed by several studies, mainly using global climate models. The common accepted picture is that since the late 1990s, the increase in anthropogenic radiative forcings has been counterbalanced by other factors, e.g., a decrease in natural forcings, augmented ocean heat storage and negative phases of ocean–atmosphere-coupled oscillation patterns. Here, simple vector autoregressive models are used for forecasting the temperature hiatus in the period 2001–2014. This gives new insight into the problem of understanding the ocean contribution (in terms of heat uptake and atmosphere–ocean-coupled oscillations) to the appearance of this recent hiatus. In particular, considering data about the ocean heat content until a depth of 700 m and the Atlantic multidecadal oscillation is necessary for correctly forecasting the hiatus, so catching both trend and interannual variability. Our models also show that the ocean heat uptake is substantially driven by the natural component of the total radiative forcing at a decadal time scale, confining the importance of the anthropogenic influences to a longer range warming of the ocean.     

Vestan lithologies mapped by the visual and infrared spectrometer on Dawn

We present global lithological maps of the Vestan surface based on Dawn mission's Visible InfraRed (VIR) Spectrometer acquisitions with a spatial sampling of 200 m. The maps confirm the results obtained with the data set acquired by VIR with a spatial sampling of 700 m, that the reflectance spectra of Vesta's surface are dominated by pyroxene absorptions that can be interpreted within the context of the distribution of howardites, eucrites, and diogenites (HEDs). The maps also partially agree with the ground and Hubble Space Telescope observations: they confirm the background surface being an assemblage of howardite or polymict eucrite, as well as the location of a diogenitic‐rich spot; however, there is no evidence of extended olivine‐rich regions in the equatorial latitudes. Diogenite is revealed on the Rheasilvia basin floor, indicating that material of the lower crust/mantle was exposed. VIR also detected diogenites along the scarp of Matronalia Rupes, and the rims of Severina and a nearby, unnamed crater, and as ejecta of Antonia crater. The diogenite distribution is fully consistent with petrological constraints; although the mapped distribution does not provide unambiguous constraints, it favors the hypothesis of a magma ocean.     

Long-lived spiral structure inN-body simulations: work in progress

Work is in progress for constructing physically consistentN-body models capable of supporting a long-lived spiral structure. Such models would represent a missing link between theory and observations of disc galaxies.     

On the relationship between Lyapunov times and macroscopic instability times

On the basis of the general theory of Hamiltonian systems, we consider the relationship between Lyapunov times and macroscopic diffusion times. We find out that there are two regimes: the Nekhoroshev regime and the resonant overlapping regime. In the first case the diffusion time is exponentially long with respect to Lyapunov times. In the second case, the relationship is polynomial although we do not find any theoretical reason for the existence of a universal power law. We show numerical evidences which confirm our theoretical considerations.     

The search for extrasolar giant planets using integral field spectroscopy: Simulations

We present here simulations of extrasolar planets detections obtained using a combination of extreme adaptive optics and integral field spectroscopy. The simulation code, written for IDL, provides images and, in particular, spectra, taking into account realistic Speckle Noise, AO correction effects and specific instrumental features. A detailed study has been done for ESO VLT telescopes (8.2 m), within the Phase A of the CHEOPS project, but the code is particularly flexible and can be updated for larger telescope diameters (ELTs) in order to give a realistic estimate of the detection limits, for giant telescopes, in standard conditions of seeing.     

The Enigmatic Behaviour of the Old Nova RR Pic

We report preliminary results of an observing run at the 1--m telescope at CTIO during which we followed RR Pic over several nights in February 2005. The resulting light curves show no sign of an eclipse. Apart from the 3.48 h period, which is usually interpreted as the orbital one, we find an additional period at P=3.78 h, which we interpret as the superhump period of the system.We furthermore present high–resolution Doppler maps in Hα, Hβ and He II, which we derived from observations at the NTT, La Silla in February 2004. They show strong variations in the emission distribution from one day to the next. While Hα and Hβ emission clearly show the accretion disc with some additional isolated sources, the He II emission is confined to an elongated region at low velocities.