Formation et évolution du Système solaire

Résumé

vignette|Disque protoplanétaire de HL Tauri (image réalisée par l'Atacama Large Millimeter Array). La formation et l'évolution du Système solaire, le système planétaire qui abrite la Terre, sont déterminées par un modèle aujourd'hui très largement accepté et connu sous le nom d'« hypothèse de la nébuleuse solaire ». Ce modèle a été développé au par Emanuel Swedenborg, Emmanuel Kant et Pierre-Simon de Laplace. Les développements consécutifs à cette hypothèse ont fait intervenir une grande variété de disciplines scientifiques comprenant l'astronomie, la physique, la géologie et la planétologie. Depuis le début de la conquête de l'espace dans les années 1950 et à la suite de la découverte des exoplanètes dans les années 1990, les modèles ont été remis en cause et affinés pour tenir compte des nouvelles observations. Selon les estimations issues de ce modèle, le Système solaire a commencé d'exister il y a 4,55 à d'années avec l'effondrement gravitationnel d'une petite partie d'un nuage

Source officielle

https://fr.wikipedia.org/wiki/Formation_et_%C3%A9volution_du_Syst%C3%A8me_solaire

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Numerical studies on saturated kink and sawtooth induced fast ion transport in JET ITER-like plasmas

Mario Podesta, Matteo Vallar

This presentation examines the energetic particle transport induced by saturated kink modes and sawtooth crashes in JET deuterium plasmas. It is known that kink mode-resonant transport and phase-space redistribution from sawtooth crashes can drive strong fast ion transport with dependencies on particle pitch and energy. Measurements with JET's Faraday cup fast ion loss detector array have shown that the internal kink growth phase preceding sawtooth crashes produces substantial fast ion losses. This report will numerically investigate the dominant energetic particle transport mechanism with a detailed examination of the fast ion phase-space dependencies, resonances, orbit topology changes, induced losses, and redistribution associated with the long-lived, resonant, kink mode and non-resonant sawtooth crash. The ORBIT-kick model forms the basis of the transport studies with realistic fast ion distributions produced from TRANSP. A recently created reduced model for sawtooth induced transport is used while the saturated kink modes are modeled with ideal magnetohydrodynamic codes. The simulations were further validated against experiment with a newly developed synthetic Faraday cup fast ion loss detector in addition to scintillator probe and neutron measurements.

IOP Publishing Ltd2022

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Extreme Deuterium Excesses in Ultracarbonaceous Micrometeorites from Central Antarctic Snow

Anders Meibom, François Robert

Primitive interplanetary dust is expected to contain the earliest solar system components, including minerals and organic matter. We have recovered, from central Antarctic snow, ultracarbonaceous micrometeorites whose organic matter contains extreme deuterium (D) excesses ( 10 to 30 times terrestrial values), extending over hundreds of square micrometers. We identified crystalline minerals embedded in the micrometeorite organic matter, which suggests that this organic matter reservoir could have formed within the solar system itself rather than having direct interstellar heritage. The high D/H ratios, the high organic matter content, and the associated minerals favor an origin from the cold regions of the protoplanetary disk. The masses of the particles range from a few tenths of a microgram to a few micrograms, exceeding by more than an order of magnitude those of the dust fragments from comet 81P/Wild 2 returned by the Stardust mission.

2010

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Identifying extant materials that act as compositional proxies for Earth is key to understanding its accretion. Copper and sulfur are both moderately volatile elements; however, they display different geochemical behavior (e.g., phase affinities). Thus, individually and together, these elements provide constraints on the source material and conditions of Earth's accretion, as well as on the timing and evolution of volatile delivery to Earth. Here we present laser-heated diamond anvil cell experiments at pressures up to 81 GPa and temperatures up to 4,100 K aimed at characterizing Cu metal-silicate partitioning at conditions relevant to core-mantle differentiation in Earth. Partitioning results have been combined with literature results for S in Earth formation modeling to constrain accretion scenarios that can arrive at present-day mantle Cu and S contents. These modeling results indicate that the distribution of Cu and S in Earth may be the result of accretion largely from material(s) with Cu contents at or above chondritic values and S contents that are strongly depleted, such as that in bulk CH chondrites, and that the majority of Earth's mass (similar to 3/4) accreted incrementally via pebble and/or planetesimal accretion. Plain Language Summary Experiments wherein molten metal and silicate (rock-building) phases unmix themselves due to their physical properties, that is, metal-silicate partitioning, can be conducted at the high temperatures and pressures (HP-HT) that characterized Earth's differentiation into a core and mantle. The redistribution of elements between the metal and silicate phases-their partitioning-during this process can be measured and mathematically described, then placed into numerical models to better understand Earth's formation history. Here we have mathematically characterized the HP-HT partitioning of copper, combined this with results for sulfur from literature, and input these characterizations into numerical models that track their distribution between Earth's core and mantle as it grows to its present mass. Copper and sulfur were chosen because they display different sensitivities to the physical mechanisms that govern planetary formation, and we can leverage this to better understand Earth's formation and differentiation history. Our results indicate that similar to 75% of Earth's precursor materials grew incrementally from relatively small bits of material-on average similar to 0.1% of Earth's mass or less-that is most compositionally similar to meteorite classes that are made up of iron-rich metal and silicate solids (chondrules) that are depleted in easily vaporized (volatile) elements, especially sulfur.

AMER GEOPHYSICAL UNION2018

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AMER GEOPHYSICAL UNION2018