scholarly journals A pebble accretion model for the formation of the terrestrial planets in the Solar System

2021 ◽  
Vol 7 (8) ◽  
pp. eabc0444 ◽  
Author(s):  
Anders Johansen ◽  
Thomas Ronnet ◽  
Martin Bizzarro ◽  
Martin Schiller ◽  
Michiel Lambrechts ◽  
...  
Keyword(s):  
Carbon Budget ◽  
Terrestrial Planet ◽  
Terrestrial Planets ◽  
The Moon ◽  
Early Generation ◽  
Isotopic Signatures ◽  
Accretion Model ◽  
Two Generations ◽  
The Masses

Pebbles of millimeter sizes are abundant in protoplanetary discs around young stars. Chondrules inside primitive meteorites—formed by melting of dust aggregate pebbles or in impacts between planetesimals—have similar sizes. The role of pebble accretion for terrestrial planet formation is nevertheless unclear. Here, we present a model where inward-drifting pebbles feed the growth of terrestrial planets. The masses and orbits of Venus, Earth, Theia (which later collided with Earth to form the Moon), and Mars are all consistent with pebble accretion onto protoplanets that formed around Mars’ orbit and migrated to their final positions while growing. The isotopic compositions of Earth and Mars are matched qualitatively by accretion of two generations of pebbles, carrying distinct isotopic signatures. Last, we show that the water and carbon budget of Earth can be delivered by pebbles from the early generation before the gas envelope became hot enough to vaporize volatiles.

scholarly journals Lunar and terrestrial planet formation in the Grand Tack scenario

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130174 ◽  
Author(s):  
S. A. Jacobson ◽  
A. Morbidelli
Keyword(s):  
Total Mass ◽  
Planet Formation ◽  
Terrestrial Planet ◽  
Terrestrial Planets ◽  
The Moon ◽  
Giant Impact ◽  
Modal Mass ◽  
The Individual ◽  
Impact Phase ◽  
Geochemical Constraints

We present conclusions from a large number of N -body simulations of the giant impact phase of terrestrial planet formation. We focus on new results obtained from the recently proposed Grand Tack model, which couples the gas-driven migration of giant planets to the accretion of the terrestrial planets. The giant impact phase follows the oligarchic growth phase, which builds a bi-modal mass distribution within the disc of embryos and planetesimals. By varying the ratio of the total mass in the embryo population to the total mass in the planetesimal population and the mass of the individual embryos, we explore how different disc conditions control the final planets. The total mass ratio of embryos to planetesimals controls the timing of the last giant (Moon-forming) impact and its violence. The initial embryo mass sets the size of the lunar impactor and the growth rate of Mars. After comparing our simulated outcomes with the actual orbits of the terrestrial planets (angular momentum deficit, mass concentration) and taking into account independent geochemical constraints on the mass accreted by the Earth after the Moon-forming event and on the time scale for the growth of Mars, we conclude that the protoplanetary disc at the beginning of the giant impact phase must have had most of its mass in Mars-sized embryos and only a small fraction of the total disc mass in the planetesimal population. From this, we infer that the Moon-forming event occurred between approximately 60 and approximately 130 Myr after the formation of the first solids and was caused most likely by an object with a mass similar to that of Mars.

Social Cohesion, Breaks, and Transformations in Italy, 535–600

2018 ◽  
Author(s):  
Walter Pohl
Keyword(s):  
The Political ◽  
Late Antique ◽  
Religious Context ◽  
Ancient Society ◽  
Complex Process ◽  
Term Change ◽  
Two Generations ◽  
Classical Culture

When the Gothic War began in Italy in 535, the country still conserved many features of classical culture and late antique administration. Much of that was lost in the political upheavals of the following decades. Building on Chris Wickham’s work, this contribution sketches an integrated perspective of these changes, attempting to relate the contingency of events to the logic of long-term change, discussing political options in relation to military and economic means, and asking in what ways the erosion of consensus may be understood in a cultural and religious context. What was the role of military entrepreneurs of more or less barbarian or Roman extraction in the distribution or destruction of resources? How did Christianity contribute to the transformation of ancient society? The old model of barbarian invasions can contribute little to understanding this complex process. It is remarkable that for two generations, all political strategies in Italy ultimately failed.

Exploring the Solar System

2018 ◽  
Author(s):  
Karel Schrijver
Keyword(s):  
Solar System ◽  
Planetary Systems ◽  
Interplanetary Dust ◽  
Terrestrial Planets ◽  
The Moon ◽  
System P ◽  
Asteroids And Comets

In this chapter, the author summarizes the properties of the Solar System, and how these were uncovered. Over centuries, the arrangement and properties of the Solar System were determined. The distinctions between the terrestrial planets, the gas and ice giants, and their various moons are discussed. Whereas humans have walked only on the Moon, probes have visited all the planets and several moons, asteroids, and comets; samples have been returned to Earth only from our moon, a comet, and from interplanetary dust. For Earth and Moon, seismographs probed their interior, whereas for other planets insights come from spacecraft and meteorites. We learned that elements separated between planet cores and mantels because larger bodies in the Solar System were once liquid, and many still are. How water ended up where it is presents a complex puzzle. Will the characteristics of our Solar System hold true for planetary systems in general?

A Culture in Crisis

2017 ◽  
Author(s):  
Erika Fischer-Lichte
Keyword(s):  
Twentieth Century ◽  
Body Ideal ◽  
The Masses ◽  
Of Greece ◽  
New Devices

Chapter 4 investigates the role of the new image of Greece in the first decades of the twentieth century. ‘A Culture in Crisis: Max Reinhardt’s Productions of Greek Tragedies (1903–1919)’ addresses two problems: first, the new body ideal and its liberation from the restraints imposed on it until then, and, second, the division within society of those who made a cult of their individuality and the rapidly growing masses of the proletariat. While in Reinhardt’s Electra (1903) Gertrud Eysoldt displayed her body as that of a maenad or a hysteric, a number of new devices were developed in Oedipus the King (1910) and the Oresteia (1911), both performed in a circus, which temporarily transformed the masses of actors and spectators into a—theatrical—community. The chapter also discusses Leopold Jessner’s production of Oedipus (1929) as a quest for a ‘philosophical theatre’ (Brecht).

The Alt-Right’s continuation of the ‘cultural war’ in Euro-American societies

Thesis Eleven ◽  
2021 ◽  
pp. 072551362110059
Author(s):  
Tamir Bar-On
Keyword(s):  
Carl Schmitt ◽  
New Right ◽  
Right Wing ◽  
Antonio Gramsci ◽  
Left Wing ◽  
Anti Semitism ◽  
The Usa ◽  
The Masses ◽  
Hearts And Minds

In this paper, I argue that the Alt-Right needs to be taken seriously by the liberal establishment, the general public, and leftist cultural elites for five main reasons: 1) its ‘right-wing Gramscianism’ borrows from the French New Right ( Nouvelle Droite – ND) and the French and pan-European Identitarian movement. This means that it is engaged in the continuation of a larger Euro-American metapolitical struggle to change hearts and minds on issues related to white nationalism, anti-Semitism, and racialism; 2) it is indebted to the metapolitical evolution of sectors of the violent neo-Nazi and earlier white nationalist movements in the USA; 3) this metapolitical orientation uses the mass media, the internet, and social media in general to reach and influence the masses of Americans; 4) the ‘cultural war’ means that the Alt-Right’s spokesman Richard Spencer, French ND leader Alain de Benoist, and other intellectuals see themselves as a type of Leninist vanguard on the radical right, which borrows from left-wing authors such as Antonio Gramsci and their positions in order to win the metapolitical struggle against ‘dominant’ liberal and left-wing political and cultural elites; and 5) this ‘cultural war’ is intellectually and philosophically sophisticated because it understands the crucial role of culture in destabilizing liberal society and makes use of important philosophers such as Friedrich Nietzsche, Carl Schmitt, Julius Evola and others in order to give credence to its revolutionary, racialist, and anti-liberal ideals.

scholarly journals Forming terrestrial planets and delivering water

2015 ◽  
Vol 11 (A29B) ◽  
pp. 427-430
Author(s):  
Kevin J. Walsh
Keyword(s):  
Planet Formation ◽  
Semimajor Axis ◽  
Giant Planet ◽  
Terrestrial Planet ◽  
Giant Planets ◽  
Asteroid Belt ◽  
Terrestrial Planets ◽  
The Earth ◽  
Building Models ◽  
Rich Material

AbstractBuilding models capable of successfully matching the Terrestrial Planet's basic orbital and physical properties has proven difficult. Meanwhile, improved estimates of the nature of water-rich material accreted by the Earth, along with the timing of its delivery, have added even more constraints for models to match. While the outer Asteroid Belt seemingly provides a source for water-rich planetesimals, models that delivered enough of them to the still-forming Terrestrial Planets typically failed on other basic constraints - such as the mass of Mars.Recent models of Terrestrial Planet Formation have explored how the gas-driven migration of the Giant Planets can solve long-standing issues with the Earth/Mars size ratio. This model is forced to reproduce the orbital and taxonomic distribution of bodies in the Asteroid Belt from a much wider range of semimajor axis than previously considered. In doing so, it also provides a mechanism to feed planetesimals from between and beyond the Giant Planet formation region to the still-forming Terrestrial Planets.

scholarly journals Life among the Craters

2004 ◽  
Vol 213 ◽  
pp. 199-202
Author(s):  
Harrison H. Schmitt
Keyword(s):  
Terrestrial Planets ◽  
The Moon ◽  
Detailed Understanding ◽  
The Earth ◽  
Planetary Mass ◽  
End Members

The Moon forms one end-member in the planetary mass series Earth-Venus-Mars-Mercury-Asteroids-Moon (Weissman 1999). Having a detailed understanding of the nature and evolution of the two end-members of this series, rather than of just the Earth, has increased the value of other data and inferences by orders of magnitude. As a consequence of obtaining an understanding of the evolution of a second planet, we now can look at other terrestrial planets with far greater insight than ever would have been possible otherwise (Fig. 1).

scholarly journals Remotely distinguishing and mapping endogenic water on the Moon

2017 ◽  
Vol 375 (2094) ◽  
pp. 20150391 ◽  
Author(s):  
Rachel L. Klima ◽  
Noah E. Petro
Keyword(s):  
Solar Wind ◽  
Spatial Distribution ◽  
Solar System ◽  
The Moon ◽  
Testing Hypotheses ◽  
Origin And Evolution ◽  
Lunar Interior ◽  
Geological Features ◽  
Insight Into

Water and/or hydroxyl detected remotely on the lunar surface originates from several sources: (i) comets and other exogenous debris; (ii) solar-wind implantation; (iii) the lunar interior. While each of these sources is interesting in its own right, distinguishing among them is critical for testing hypotheses for the origin and evolution of the Moon and our Solar System. Existing spacecraft observations are not of high enough spectral resolution to uniquely characterize the bonding energies of the hydroxyl molecules that have been detected. Nevertheless, the spatial distribution and associations of H, OH − or H 2 O with specific lunar lithologies provide some insight into the origin of lunar hydrous materials. The global distribution of OH − /H 2 O as detected using infrared spectroscopic measurements from orbit is here examined, with particular focus on regional geological features that exhibit OH − /H 2 O absorption band strengths that differ from their immediate surroundings. This article is part of the themed issue ‘The origin, history and role of water in the evolution of the inner Solar System’.

Sir Charles Dilke and the British Intervention In Egypt, 1882: decision making In a nineteenth-century cabinet

1976 ◽  
Vol 2 (3) ◽  
pp. 231-245 ◽  
Author(s):  
M. E. Chamberlain
Keyword(s):  
Nineteenth Century ◽  
Decision Making ◽  
British Imperialism ◽  
Exact Role ◽  
The Unconscious ◽  
William Gladstone ◽  
Two Generations ◽  
Liberal Government

“There's Dilke that has done it all”, remarked Wilfrid Scawen Blunt to Lord Blandford as they watched Dilke walk down Piccadilly one day in July 1882.1 The “it” was the British intervention in Egypt which entangled Britain in Egyptian affairs for two generations. More soberly, Louis Mallet, the Permanent Under-Secretary at the India Office, wrote to Evelyn Baring a year later that the Liberal government of William Gladstone had made themselves “the unconscious, and some of them (not all) the unwilling instruments of a policy from which Lord Beaconsfield and Lord Salisbury would have shrunk, and which is big with future disaster”. “Dilke and Chamberlain” he wrote, “I consider mainly responsible for the Egyptian war.” In The Trouble Makers, A. J. P. Taylor came to the conclusion, “The occupation of Egypt in 1882 marked Gladstone's decisive breach with Radicalism. Indeed it ruined Radicalism for more than a generation. It began modern British Imperialism…”. How ironic if the ruin of British radicalism was brought about by the two leading radicals of Gladstone's predominantly Whig administration. What do the Dilke and Chamberlain papers among others reveal about the exact role of the two men in the crisis ?

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