Ablation of Ni from micrometeoroids in the upper atmosphere: Experimental and computer simulations and implications for Fe ablation

Modelling the ablation of Ni from micrometeoroids upon their entry to the Earth’s atmosphere enables us to better understand not just the Ni layers in the upper atmosphere but also the differential ablation of Fe. A new version of our meteoroid ablation model has been developed that includes a metal phase in addition to the existing silicate phase. The validity of this new model has been verified via laboratory experiments of Ni ablation. Meteoritic particles (powdered terrestrial meteorites) and mineral proxies were flash heated to temperatures as high as 2700 K to simulate atmospheric entry. Slower linear heating ramps were also conducted to allow a more precise study of ablation as a function of temperature. Ni ablates rapidly, shortly after Na, which was used here as a reference. The model reproduces the experimental results generally within experimental error. Disagreement between the model and the data can be explained by the distribution of Ni in small grains in the meteorite samples, in contrast to the model assumptions of one molten metal phase. Small grain sizes are consistent with the Fe–Ni grain size observed in SEM-EDX mapping of the meteorite particles used for this study.