PRODUCTION OF SYNTHETIC METEORITE SPHERES USING AERODYNAMIC LEVITATION COMBINED WITH LASER HEATING

Studies of the detailed chemistry, mineralogy, and isotopic compositions of meteorites provide invaluable clues to the range of chemical and physical processes and timing of events in the solar nebula. To study meteorites, scientists often use analytical methods that alter or destroy these valuable samples. The creation of synthetic meteorites helps alleviate this problem. This study uses a High Temperature Conical Nozzle Levitation (HT-CNL) system, combining laser heating with aerodynamic levitation, to create synthetic meteorites that reproduce the compositions and textures of natural meteorites.

We combined powdered compounds (e.g., MgO, SiO₂, Fe₂O₃, etc.) in proportions matching the compositions of natural EL and CI chondrites and in simplified analogues (e.g., Fe-free). The powder mixtures are weighed out, fused to form spheres in a Cu-hearth plate, and then levitated on a flow of gas above a conical nozzle while being heated with a 400 W CO₂ laser. The synthesis experiments were conducted at temperatures between 1600 and 2200 ^°C, heating times between 5-240 s, and in levitation gases of pure Ar, pure O₂, or a mixture of CO and CO₂. Each variable has an effect on the outcome of the experiment and can help inform the conditions attending meteorite formation and alteration.

Fe-bearing synthetic chondrite spheres have rough, metallic external surfaces and contain dendritic Fe-metal crystals inside. Visual comparisons of these synthetic spheres with some natural samples reveal striking similarities, suggesting that our technique likely produces good analogues. One application of our experiments is to investigate mass loss due to volatilization at high T. Preliminary evaporation experiments using Fe-bearing chondrite compositions resulted in <6% mass loss, whereas Fe-free compositions had up to 12% mass loss. Comparing the levitation conditions and results of both Fe-bearing and Fe-free experiments, we determined that Fe-bearing spheres had significantly less mass loss than Fe-free spheres, and that Fe-free spheres had a positive correlation with mass loss, heating time, and temperature. There is no apparent correlation between mass loss and levitation gas mixture for either composition. Future work will involve isotopic analyses of these experiments to learn about evaporation induced fractionation.