Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed seventeen Ryugu samples measuring 1-8 mm. CO 2 -bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and Ca, Al-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed by aqueous alteration reactions at low temperature, high pH, and water/rock ratios < 1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate Ryugu’s parent body formed ~ 2 million years after the beginning of Solar System formation.

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Detection of rare earth elements (REE) is commonly performed with destructive techniques such as (LA)-ICP-MS or coupled to a destructive sample preparation. When investigating unique geological samples, such as cometary, asteroidal or interstellar material from sample return missions or inclusions in deep-Earth diamonds, a non-destructive method is preferred. The presented non-destructive highly sensitive wavelength-dispersive X-ray fluorescence spectroscopy (WD-XRF) technique is designed to measure the L-lines of REE between 4.5 and 7 keV with a sensitivity down to the ppm level. REE fluorescence L-lines are often only separated by a few eV from neighboring XRF lines and cannot be resolved by an energy dispersive approach especially in the presence of transition metal K lines. In our spectrometer the characteristic X-rays emitted by the sample are dispersed by a fixed Ge(111) analyzer crystal over the active area of an energy dispersive pnCCD detector, enabling high energy resolution detection of X-rays differentiated by their corresponding Bragg angles. The use of an energy-dispersive 2D detector enables to simultaneously acquire XRF lines while eliminating any ambiguities due to potential contribution from higher order diffraction effects or other diffraction planes, and thereby increases the sensitivity by reducing the (scatter) background. This detection method shows an energy resolution of 12 eV for the Ti-Kα fluorescence line and has a sensitivity down to 0.50 ppm for REE L-lines. The method was optimized specifically for the non-destructive analysis of inclusions in deep Earth diamonds, yielding in situ quantitative information about up-to-now inaccessible elemental (REE) composition patterns together with the more abundant transition metals like Ti, Cr, Mn and Fe. This information is of great importance to decipher the role that deep Earth plays in the global carbon and fluid cycle.

Chondrules are thought to play a crucial role in planet formation, but the mechanisms leading to their formation are still a matter of unresolved discussion. So far, experiments designed to understand chondrule formation conditions have been carried out only under the influence of terrestrial gravity. In order to introduce more realistic conditions, we developed a chondrule formation experiment, which was carried out at long‐term microgravity aboard the International Space Station. In this experiment, freely levitating forsterite (Mg2SiO4) dust particles were exposed to electric arc discharges, thus simulating chondrule formation via nebular lightning. The arc discharges were able to melt single dust particles completely, which then crystallized with very high cooling rates of >105 K h−1. The crystals in the spherules show a crystallographic preferred orientation of the [010] axes perpendicular to the spherule surface, similar to the preferred orientation observed in some natural chondrules. This microstructure is probably the result of crystallization under microgravity conditions. Furthermore, the spherules interacted with the surrounding gas during crystallization. We show that this type of experiment is able to form spherules, which show some similarities with the morphology of chondrules despite very short heating pulses and high cooling rates.

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