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Experimental and stable isotope constraints on the accretion and differentiation of the terrestrial planets

English title Experimental and stable isotope constraints on the accretion and differentiation of the terrestrial planets
Applicant Sossi Paolo
Number 180025
Funding scheme Ambizione
Research institution Institut für Geochemie und Petrologie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geochemistry
Start/End 01.01.2019 - 31.12.2022
Approved amount 842'820.00
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All Disciplines (2)

Discipline
Geochemistry
Astronomy, Astrophysics and Space Sciences

Keywords (6)

Experiments; Thermodynamics; Volatile elements; Planet formation; Stable Isotopes; Evaporation

Lay Summary (Italian)

Lead
Malgrado la distinzione grossolana tra i pianeti, passando da corpi rocciosi all’interno del Sistema solare (per esempio, Venere o Marte), ai pianeti giganti composti maggiormente di gas come Giove, le ragioni che contribuiscono a questa varietà non sono ben definite. I pianeti hanno subito vari processi durante la loro formazione, tra cui gli impatti tra due corpi planetari. Nonostante che le collisioni causino della fusione estesa sul pianeta, il loro effetto sulla sua composizione è poco conosciuto. L’obbiettivo del progetto è di sviluppare un programma sperimentale che permetterebbe di studiare la vaporizzazione degli elementi moderatamente volatili dai pianeti rocciosi per meglio costringere le loro condizioni (temperatura, pressione, e fugacità d’ossigeno) di formazione.
Lay summary

Nella cosmochimica, le temperature di condensazione degli elementi rappresentano una scala che descrive la "volatilità" di un elemento, cioè, la sua tendenza di essere in uno stato gassoso. Però, questa scala è quantitativa solo su condizioni specifiche ; quelle della nebula solare. Ciò nonostante, le temperature di condensazione sono state usate per capire il comportamento di un elemento durante la formazione della Terra ed altri pianeti, anche se le condizioni su cui si sono formate divergono di quelle della nebula solare. Come risultato, c’è bisogno di caratterizzare le proprietà degli elementi durante la loro vaporizzazione su altre condizioni che sono più rilevanti.

Lo scopo del progetto è di fare degli sperimenti che simulano la vaporizzazione dei pianeti e di quantificare la volatilità degli elementi durante questo processo. Per raggiungere quest’obbiettivo, delle composizioni basaltiche/peridotitiche saranno subite ad una variazione sistematica di temperatura, pressione, e fugacità d’ossigeno in un forno d’atmosfera controllata. Gli sperimenti saranno analizzati chimicamente, isotopicamente e con la spettroscopia di raggi-X per stabilire la struttura e le proprietà degli elementi moderatamente volatili nei melt silicati. L’obbiettivo sarà di sviluppare un formalismo fisico che spiega le osservazioni sperimentali. Questo formalismo potrebb'essere utilizzato per calcolare le condizioni subite dai pianeti rocciosi. Al di là, quest’approccio producerà dei dati termodinamici che servono in altri contesti di alta temperatura, nonché predire l’effetto chimico della vaporizzazione sui pianeti


Direct link to Lay Summary Last update: 18.01.2019

Responsible applicant and co-applicants

Employees

Publications

Publication
An experimentally-determined general formalism for evaporation and isotope fractionation of Cu and Zn from silicate melts between 1300 - 1500 °C and 1 bar
, An experimentally-determined general formalism for evaporation and isotope fractionation of Cu and Zn from silicate melts between 1300 - 1500 °C and 1 bar, in Geochimica et Cosmochimica Acta, N/A-N/A.

Collaboration

Group / person Country
Types of collaboration
National Centre of Competence in Research PlanetS, Bern Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
University of Bern Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Swiss Lightsource - SLS Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
EGU 2020 Talk given at a conference A Venus-like atmosphere on the early Earth from magma ocean outgassing 04.05.2020 Virtual Meeting, Austria Sossi Paolo;
CRPG Seminar Series Individual talk Tidal pull of the Earth strips the Moon of its volatiles 23.01.2020 CRPG, Universite de Lorraine, Nancy, France Sossi Paolo;
GeoMunster Talk given at a conference Keynote: Mechanics and conditions for devolatilising the Moon 25.09.2019 Munster, Germany Sossi Paolo;
EPSC-DPS 2019 Talk given at a conference Tidal pull of the Earth strips the Moon of its volatiles from a surface magma ocean 17.09.2019 Geneva, Switzerland Sossi Paolo;
Goldschmidt 2019 Talk given at a conference Invited: The Oxidation State of Iron in Peridotite Liquids and Implications for Planetary Magma Oceans 19.08.2019 Barcelona, Spain Sossi Paolo;


Self-organised

Title Date Place

Abstract

I aim to investigate the conditions - T, P, fO2 - of volatile depletion during planet formation with a two-fold experimental and stable isotopic approach.Moderately volatile elements or MVEs are ideal for this objective, because they are sub-equally distributed between the condensed- and gas phases. They comprise a diverse group of elements (e.g., Na, Cd, Mn, Rb, Ge), classified by their behaviour in the solar nebula where, at equilibrium, they condense after the major elements, Si, Fe and Mg (1350 K), but before FeS (650 K). Nebular condensation from a cooling disk should result in a progressive increase in MVE abundances in celestial bodies with distance from the Sun. Although this holds for chondrites, planetary bodies have more complex patterns, suggesting that post-nebular processes, such as collisional erosion or core formation, play a role in determining planetary MVE budgets. Evaporation, caused by impact-heating, is hypothesised to account for the volatile-poor Moon, on the basis of elemental and stable isotope signatures. However, because condensation is equivalent to evaporation only at equilibrium, and because the temperature (T), pressure (P) and oxygen fugacity (fO2) during planetary collisions differ greatly from that of the solar nebula, the nature of post-nebular volatile depletion cannot yet be quantified for lack of experiments.Volatility experiments on the evaporation of moderately volatile elements from natural silicate melts under controlled P, T and fO2 will provide the basis for the project. The experiments will be performed in i) an open system and ii) a closed system to quantify the kinetic and equilibrium thermodynamic properties, respectively, of MVEs at conditions relevant to planetary accretion. The products of the volatility experiments will be subject to three stages of analysis:1)Major and trace element abundances. The budget of MVEs remaining in the glass (open-system) and glass and condensate (closed-system) experiments will be determined by Electron Probe Micro Analysis (EPMA) and Laser-Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS). The data will be fit by kinetic (Hertz-Knudsen-Langmuir theory) and equilibrium (Gibbs Free Energy) models to characterise MVE volatility.2)X-Ray Absorption Fine Structure (XAFS). Information on bond lengths and oxidation states of selected MVEs in the experimental glasses will be obtained by XAFS. This will guide data fitting by identifying the stable species in the condensed phase, and how it is influenced by temperature and oxygen fugacity.3)Stable isotopic composition. Measurement of stable isotope fractionation of elements over a variety of volatilities and redox states (Ca, V, Si, Fe, Cu, Zn) by wet-chemical dissolution and chromatographic methods. The results will be modelled using constraints from bonding environment in the glasses from XAFS and ab-initio molecular dynamic simulations and be used to interpret stable isotope signatures in terrestrial, lunar, and meteoritic rocks. The thermodynamic and isotopic information on the behaviour of MVEs in liquids and gases obtained will be employed in conjunction with numerical models of impacts, in order to quantify the physical-chemical conditions at which planet formation occurred. Together, these complementary techniques have the potential to provide a holistic view of the accretion of the terrestrial planets.
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