Characterization of the Extraterrestrial Magnesium Source in the Atmosphere Using a Meteoric Ablation Simulator

Ablation of Mg from meteoroids entering the Earth's atmosphere was studied experimentally using a Meteoric Ablation Simulator: micron‐sized particles of representative meteoritic material were flash heated to simulate atmospheric entry and the ablation rate of Mg with respect to Na measured by fast time‐resolved laser‐induced fluorescence. Over the range of particle diameters and entry velocities studied, Mg ablates 4.3 ± 2.1 times less efficiently than Na and 2.4 ± 0.8 times less efficiently than Fe. The resulting evaporation profiles indicate that Mg mostly ablates around 84 km in the atmosphere, compared with Fe at 88 km and Na at 95 km. The chemical ablation model Chemical Ablation Model predicts satisfactorily the measured peak ablation altitudes and relative ablated fractions of Mg, Na, Fe, and Ca but does not capture the breadth of the ablation profiles, probably due to the inhomogeneity of the minerals present in meteoroids combined with experimental limitations. Plain Language Summary About 40 t of cosmic dust enters the Earth's atmosphere every day. These meteoroids, which contain minerals composed of metallic elements such as iron, sodium, calcium, and magnesium enter the Earth's atmosphere at high speeds (between 24,000 and 160,000 mph). The resulting flash heating caused by high‐energy impacts with air molecules can lead to melting and in some cases complete evaporation of the particles—a process termed ablation. In this study, ablation is simulated using particles from different types of meteorite which are rapidly heated to well over 1700°C (3100°F) during the few seconds this would occur in the atmosphere. Lasers probe the resulting evaporation of a variety of metals. Here we show that magnesium evaporates less efficiently and at lower altitudes than sodium and iron, which is consistent with the predicted thermodynamics of the molten particles. Key Points Differential ablation of Mg with respect to Na, Fe, and Ca observed from a range of meteoritic samples Experimental simulations confirm predictions of a chemical ablation model based on melt thermodynamics and Langmuir evaporation Mg should mostly ablate in the atmosphere between 80 and 90 km, with an ablation peak 4 km below that of Fe and 11 km below Na