Meteoroid atmospheric entry investigated with plasma flow experiments: Petrography and geochemistry of the recovered material
Lidia Pittarello, Steven Goderis, Bastien Soens, Seann J. McKibbin, Gabriele Giuli, Federico Bariselli, Bruno Dias, Bernd Helber, Giovanni O. Lepore, Frank Vanhaecke, Christian Koeberl, Thierry E. Magin, Philippe Claeys
In Press, Accepted Manuscript, Available online 2 May 2019
• Atmospheric entry of asteroidal material reproduced in high enthalpy experiments.
• The glass produced by melting basalt and an ordinary chondrite was recovered.
• Characteristic features of natural meteorite fusion crusts were reproduced.
• Alkali metals are vaporized, the glass is enriched in moderately siderophile elements.
• Redox equilibrium independent from original oxidation state”
“Melting experiments attempting to reproduce some of the processes affecting asteroidal and cometary material during atmospheric entry have been performed in a high enthalpy facility. For the first time with the proposed experimental setup, the resulting material has been recovered, studied, and compared with natural analogues, focusing on the thermal and redox reactions triggered by interaction between the melt and the atmospheric gases under high temperature and low pressure conditions. Experimental conditions were tested across a range of parameters, such as heat flux, experiment duration, and pressure, using two types of sample holders materials, namely cork and graphite. A basalt served as asteroidal analog and to calibrate the experiments, before melting a H5 ordinary chondrite meteorite. The quenched melt recovered after the experiments has been analyzed by μ-XRF, EDS-SEM, EMPA, LA-ICP-MS, and XANES spectroscopy.
The glass formed from the basalt is fairly homogeneous, depleted in highly volatile elements (e.g., Na, K), relatively enriched in moderately siderophile elements (e.g., Co, Ni), and has reached an equilibrium redox state with a lower Fe3+/Fetot ratio than that in the starting material. Spherical objects, enriched in SiO2, Na2O and K2O, concentrations, were observed, inferring condensation from the vaporized material. Despite instantaneous quenching, the melt formed from the ordinary chondrite shows extensive crystallization of mostly olivine and magnetite, the latter indicative of oxygen fugacity compatible with presence of both Fe2+ and Fe3+. Similar features have been observed in natural meteorite fusion crusts and in micrometeorites, implying that, at least in terms of maximum temperature reached and chemical reactions, the experiments have successfully reproduced the conditions likely encountered by extraterrestrial material following atmospheric entry.”