Carbonated Chondrites during Giant ImpactsOPEN ACCESS 

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Adrien Saurety and Razvan Caracas

The Planetary Science Journal, Volume 7, Number 3

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“The volatile budget of terrestrial planets is primarily inherited from the accretion process. At this stage, impacts played a significant role in delivering or removing volatiles from the silicate of young planets. Among those volatile elements, carbon is particularly interesting, as it is thought to be abundant in the early solar system but depleted in the mantles of the terrestrial planets. In this study, we investigate the shock response of a carbonated silicate representative of the early solar system using ab initio molecular dynamics (AIMD). We found that the CO2 addition in the silicate decreases its initial density, which contributes to modifying the Hugoniot curve. We used the radius of the first coordination sphere to compute the speciation of C in the melt along the Hugoniot curve. We note the formation of iron and silicon carbide under certain conditions during the AIMD run. To further investigate the chemical bonding between C and Fe, as well as between C and Si, we computed the electron localization function (ELF). This analysis revealed that C–Fe and C–Si are covalently bonded. We also used the ELF to investigate the breaking of the C–Fe bond. Our results showed that the interatomic distance is not a relevant criterion for computing the chemical speciation in AIMD simulations. Only a proper vibration is characteristic of an electronic exchange. Using a lifetime cutoff value, we showed that the number of reduced carbon atoms increases along the Hugoniot curve. This formation of reduced species could have significant implications for the redox state of silicate melts under shock conditions.”

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