Séminaire «Temps et Espace» (IMCCE et SYRTE)
An atomic-scale perspective on the Giant Impact and the protolunar disk
Razvan Caracas – ENS
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The early age of the solar system has seen numerous giant impacts, on a scale energetic enough to make and unmake planetesimals and moons. The Earth did not escape to this pattern; the last giant impact must have been large enough to transform the proto-Earth and the impactor, Theia, into a protolunar disk from which later on the actual Earth and the Moon condensed.
Some of the most important thermodynamic parameters that are necessary in the modeling of such and impact, and that are also missing today, are the positions of the critical points, the liquid-vapor equilibria, and the equation of state for both liquids and the supercritical fluids.
To study this region, we employ large-scale first-principles molecular dynamics simulations. We consider the average composition of the Earth’s mantle and we cover the 0.75 – 7.5 g/cm3 density range and 2000 – 10000 K temperature range. This allows us to investigate the thermodynamics conditions ranging throughout the entire disk, from the interior of the molten core to the outer regions of the vaporized disk, to identify and characterize the supercritical region and to discuss the effect of a selected collection of volatiles on the structure and properties of the disk.