ISTerre seminar

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Metal fragmentation by Rayleigh-Taylor instabilities during Earth-Forming collisions

Tuesday 11 June 2024 - 11h00

Augustin Maller - Institut de Physique du Globe de Paris
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The long-term evolution of the Earth depends on its initial composition and temperature. These were set by the large planetary collisions that formed the Earth. Under certain conditions, the iron core of the impactor could have fragmented into drops during the impact or later in the magma ocean. The size of these drops controlled the efficiency of chemical transfers between metal and silicates and as a consequence the initial composition of the Earth. In this study, we investigate the size of the drops formed upon impact with analog laboratory experiments. We study the impact of a centimeter-sized liquid volume onto a pool of a lighter immiscible liquid at large Weber numbers. We show that the instabilities during the opening of the crater are likely to be Rayleigh-Taylor instabilities and we then obtain a predictive scaling law on the average size as a function of the impact parameters. This scaling law predicts for Earth-forming collisions sub milimetric drops when fragmentation is possible upon impact ensuring total equilibration of the impactor core.

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Organizing team : Géodynamo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères