Remembering Michèle Moons     

Alessandro Morbidelli 《Celestial Mechanics and Dynamical Astronomy》1998,68(3):199-204

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Basaltic volcanism in the northern sector of the main Ethiopian rift     

P. Brotzu  M. T. Ganzerli-Valentini  L. Morbidelli  E. M. Piccirillo  R. Stella  G. Traversa 《Journal of Volcanology and Geothermal Research》1981,10(4):365-382

The different basalt types related to rift structure development have been investigated, starting from the pre-rift stage in the northern Ethiopian rift and its eastern escarpment and plateau.The basic volcanic rocks are represented mainly by transitional basalts, both in the pre-rift (plateau) and rift (escarpment and rift floor) stages. A striking feature is that although the plateau basalts show clear tholeiitic affinity and the rift basalts reveal a somewhat pronounced “alkaline” character, the REE and LILE element abundances, however, progressively decrease from the “tholeiitic” basalts of the plateau to the “alkaline” basalts of the rift.All data support the view that such contrasting features may be attributed to a continuous depletion of hygromagmatophile (REE, LILE) elements in the mantle source material, related to the large volumes of magmas produced in the early phase of rift structure development. The transition from “tholeiitic” (plateau) to “alkaline” (rift) transitional basalts is related to decreasing intensity of extensional movements.  相似文献   

Transitional basalts of alkaline or tholeiitic affinity in the somali trap series (southeastern margin of the main Ethiopian rift from 8° 10′ to 8° 70′ Lat. N)     

P. Brotzu  L. Morbidelli  E. M. Piccirillo  G. Traversa 《Bulletin of Volcanology》1974,38(1):254-269

The Trap Series outcropping in the southeastern margin of the Main Ethiopian Rift has a total thickness of not less than 500–600 m. In this series, mainly composed of flood lavas and rare scoriaceous beds, basaltic rocks — which on a serial viewpoint are transitional basalts — are the best represented. Alkali-olivine basalts (with modal and normative nepheline) are interbedded within the lower and middle members of the series, while in the upper members andesine basalts and dark phonolitic tephrites are present. Among the transitional basalts, rocks of alkaline and of tholeiitic affinity are present as shown by petrographic and chemical analyses. On the basis of petrochemical and geovolcanological data, it is probable that these rocks and the phonolitic-tephrites originated from different primary magmas.  相似文献   

The primordial excitation and clearing of the asteroid belt—Revisited     

David P. O'Brien  Alessandro Morbidelli 《Icarus》2007,191(2):434-452

We have performed new simulations of two different scenarios for the excitation and depletion of the primordial asteroid belt, assuming Jupiter and Saturn on initially circular orbits as predicted by the Nice Model of the evolution of the outer Solar System [Gomes, R., Levison, H.F., Tsiganis, K., Morbidelli, A., 2005. Nature 435, 466-469; Tsiganis, K., Gomes, R., Morbidelli, A., Levison, H.F., 2005. Nature 435, 459-461; Morbidelli, A., Levison, H.F., Tsiganis, K., Gomes, R., 2005. Nature 435, 462-465]. First, we study the effects of sweeping secular resonances driven by the depletion of the solar nebula. We find that these sweeping secular resonances are incapable of giving sufficient dynamical excitation to the asteroids for nebula depletion timescales consistent with estimates for solar-type stars, and in addition cannot cause significant mass depletion in the asteroid belt or produce the observed radial mixing of different asteroid taxonomic types. Second, we study the effects of planetary embryos embedded in the primordial asteroid belt. These embedded planetary embryos, combined with the action of jovian and saturnian resonances, can lead to dynamical excitation and radial mixing comparable to the current asteroid belt. The mass depletion driven by embedded planetary embryos alone, even in the case of an eccentric Jupiter and Saturn, is roughly 10-20× less than necessary to explain the current mass of the main belt, and thus a secondary depletion event, such as that which occurs naturally in the Nice Model, is required. We discuss the implications of our new simulations for the dynamical and collisional evolution of the main belt.  相似文献   

Onset of secular chaos in planetary systems: period doubling and strange attractors     

Konstantin Batygin  Alessandro Morbidelli 《Celestial Mechanics and Dynamical Astronomy》2011,111(1-2):219-233

As a result of resonance overlap, planetary systems can exhibit chaotic motion. Planetary chaos has been studied extensively in the Hamiltonian framework, however, the presence of chaotic motion in systems where dissipative effects are important, has not been thoroughly investigated. Here, we study the onset of stochastic motion in presence of dissipation, in the context of classical perturbation theory, and show that planetary systems approach chaos via a period-doubling route as dissipation is gradually reduced. Furthermore, we demonstrate that chaotic strange attractors can exist in mildly damped systems. The results presented here are of interest for understanding the early dynamical evolution of chaotic planetary systems, as they may have transitioned to chaos from a quasi-periodic state, dominated by dissipative interactions with the birth nebula.  相似文献   

Quantitative perturbation theory by successive elimination of harmonics     

Alessandro Morbidelli  Antonio Giorgilli 《Celestial Mechanics and Dynamical Astronomy》1993,55(2):131-159

We revisit some results of perturbation theories by a method of successive elimination of harmonics inspired by some ideas of Delaunay. On the one hand, we give a connection between the KAM theorem and the Nekhoroshev theorem. On the other hand, we support in a quantitative fashion a semi-numerical method of analysis of a perturbed system recently introduced by one of the authors.  相似文献   

On the width and shape of gaps in protoplanetary disks     

A. Crida  A. Morbidelli 《Icarus》2006,181(2):587-604

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3. Solar System Formation and Early Evolution: the First 100 Million Years     

Thierry Montmerle  Jean-Charles Augereau  Marc Chaussidon  Mathieu Gounelle  Bernard Marty  Alessandro Morbidelli 《Earth, Moon, and Planets》2006,98(1-4):39-95

The solar system, as we know it today, is about 4.5 billion years old. It is widely believed that it was essentially completed 100 million years after the formation of the Sun, which itself took less than 1 million years, although the exact chronology remains highly uncertain. For instance: which, of the giant planets or the terrestrial planets, formed first, and how? How did they acquire their mass? What was the early evolution of the “primitive solar nebula” (solar nebula for short)? What is its relation with the circumstellar disks that are ubiquitous around young low-mass stars today? Is it possible to define a “time zero” (t ₀), the epoch of the formation of the solar system? Is the solar system exceptional or common? This astronomical chapter focuses on the early stages, which determine in large part the subsequent evolution of the proto-solar system. This evolution is logarithmic, being very fast initially, then gradually slowing down. The chapter is thus divided in three parts: (1) The first million years: the stellar era. The dominant phase is the formation of the Sun in a stellar cluster, via accretion of material from a circumstellar disk, itself fed by a progressively vanishing circumstellar envelope. (2) The first 10 million years: the disk era. The dominant phase is the evolution and progressive disappearance of circumstellar disks around evolved young stars; planets will start to form at this stage. Important constraints on the solar nebula and on planet formation are drawn from the most primitive objects in the solar system, i.e., meteorites. (3) The first 100 million years: the “telluric” era. This phase is dominated by terrestrial (rocky) planet formation and differentiation, and the appearance of oceans and atmospheres.  相似文献   

Considerations on the magnitude distributions of the Kuiper belt and of the Jupiter Trojans     

Alessandro Morbidelli  Harold F. Levison  Luke Dones 《Icarus》2009,202(1):310-315

By examining the absolute magnitude (H) distributions (hereafter HD) of the cold and hot populations in the Kuiper belt and of the Trojans of Jupiter, we find evidence that the Trojans have been captured from the outer part of the primordial trans-neptunian planetesimal disk. We develop a sketch model of the HDs in the inner and outer parts of the disk that is consistent with the observed distributions and with the dynamical evolution scenario known as the ‘Nice model’. This leads us to predict that the HD of the hot population should have the same slope of the HD of the cold population for 6.5<H<9, both as steep as the slope of the Trojans' HD. Current data partially support this prediction, but future observations are needed to clarify this issue. Because the HD of the Trojans rolls over at H∼9 to a collisional equilibrium slope that should have been acquired when the Trojans were still embedded in the primordial trans-neptunian disk, our model implies that the same roll-over should characterize the HDs of the Kuiper belt populations, in agreement with the results of Bernstein et al. [Bernstein, G.M., and 5 colleagues, 2004. Astron. J. 128, 1364-1390] and Fuentes and Holman [Fuentes, C.I., Holman, M.J., 2008. Astron. J. 136, 83-97]. Finally, we show that the constraint on the total mass of the primordial trans-neptunian disk imposed by the Nice model implies that it is unlikely that the cold population formed beyond 35 AU.  相似文献   

Asteroidal source of L chondrite meteorites     

David Nesvorný  David Vokrouhlický  Alessandro Morbidelli  William F. Bottke 《Icarus》2009,200(2):698-701

Establishing connections between meteorites and their parent asteroids is an important goal of planetary science. Several links have been proposed in the past, including a spectroscopic match between basaltic meteorites and (4) Vesta, that are helping scientists understand the formation and evolution of the Solar System bodies. Here we show that the shocked L chondrite meteorites, which represent about two thirds of all L chondrite falls, may be fragments of a disrupted asteroid with orbital semimajor axis a=2.8 AU. This breakup left behind thousands of identified 1–15 km asteroid fragments known as the Gefion family. Fossil L chondrite meteorites and iridium enrichment found in an ≈467 Ma old marine limestone quarry in southern Sweden, and perhaps also ∼5 large terrestrial craters with corresponding radiometric ages, may be tracing the immediate aftermath of the family-forming collision when numerous Gefion fragments evolved into the Earth-crossing orbits by the 5:2 resonance with Jupiter. This work has major implications for our understanding of the source regions of ordinary chondrite meteorites because it implies that they can sample more distant asteroid material than was previously thought possible.  相似文献