Experimental Chondrule Formation I - Lightning Discharge Experiments under Microgravity Conditions at the International Space Station
Astrophysics and Astronomy
Final Report Abstract
The initial aim of the project was to answer the question if lightning is a reliable process of chondrule formation, in order to test the "nebular lightning theory”. As chondrules are one of the few main components formed in the early Solar Nebula it will help to understand the formation mechanism of our Solar System. After we successfully performed lightning experiments under long-term gravity on board of the International Space Station – ISS this part of the project was to analyse the particles formed with various analytical techniques like transmission and scanning electron microscopy, electron backscatter diffraction, synchrotron X-ray CT and XRD and bring these results in context with the formation of the earliest solids formed and processed in the Solar Nebula. The publications which are based on the outcome of this project show that we were able to: a) develop and design a successful experimental set-up b) perform comprehensive experimental pre-tests on Earth c) transfer this knowledge to successfully perform experiments under long-term gravity aboard the ISS d) perform methodically complex and comprehensive analyses of the sample material after it was brought back to Earth. The main results of the project are that: a) such experiments can only be carried out efficiently in long-lasting microgravity, i.e. that drop tower experiments or parabolic flights are only conditionally suitable for investigating chondrule formation in arc experiments b) merging of dust particles takes place even with comparatively low energy inputs c) the microstructure and morphology of the (partially) melted grains is very diverse d) the microstructure and morphology of the melted particles are in part very similar to those of natural chondrules e) the structures from complex aggregates formed during this experiment can be used to better understand and explain the formation of fluffy-type CAIs, the oldest known solids of our Solar System, and their survival during incorporation into asteroids. In summary, our experiments have shown that the "nebular lightning" theory is amenable to experimental verification. However, since we could only send one experimental setup to the ISS, we could only study dust grains with a simple chemical composition (i.e. forsterite). This excludes some of the microstructures and morphologies observed in natural chondrules. The second (rejected) project would have given reason to expect further insights.
Publications
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Überflieger - A Student Competition for ISS Experiments. Proceedings of the 68th IAC (International Astronautical Congress) 2017, IAC-17, E1, 3, 12, x37659, 12pp
Weppler et al.
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A chondrule formation experiment aboard the ISS: Experimental set-up and test experiments. Icarus, 350 (2020, 11), 113898.
Spahr, Dominik; Koch, Tamara E.; Merges, David; Beck, Anna A.; Bohlender, Bernhard; Carlsson, Johan M.; Christ, Oliver; Fujita, Shintaro; Genzel, Philomena-Theresa; Kerscher, Jochen; Knautz, Tobin; Lindner, Miles; Mederos, Leber Diego; Milman, Victor; Morgenroth, Wolfgang; Wilde, Fabian; Brenker, Frank E. & Winkler, Björn
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Formation of chondrule analogs aboard the International Space Station. Meteoritics & Planetary Science, 56(9), 1669-1684.
Koch, Tamara E.; Spahr, Dominik; Tkalcec, Beverley J.; Lindner, Miles; Merges, David; Wilde, Fabian; Winkler, Björn & Brenker, Frank E.
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Mg2SiO4 particle aggregation aboard the ISS. Astronomy & Astrophysics, 653 (2021, 8, 31), A1.
Koch, T. E.; Spahr, D.; Merges, D.; Winkler, B. & Brenker, F. E.
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A chondrule formation experiment aboard the ISS: microtomography, scanning electron microscopy and Raman spectroscopy on Mg$$_2$$SiO$$_4$$ dust aggregates. Physics and Chemistry of Minerals, 49(5).
Spahr, Dominik; Koch, Tamara E.; Merges, David; Bayarjargal, Lkhamsuren; Genzel, Philomena-Theresa; Christ, Oliver; Wilde, Fabian; Brenker, Frank E. & Winkler, Björn
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Formation of fused aggregates under long‐term microgravity conditions aboard the ISS with implications for early solar system particle aggregation. Meteoritics & Planetary Science, 57(6), 1174-1193.
Koch, Tamara E.; Spahr, Dominik; Tkalcec, Beverley J.; Christ, Oliver; Genzel, Philomena‐Theresa; Lindner, Miles; Merges, David; Wilde, Fabian; Winkler, Björn & Brenker, Frank E.
