Chemical assessment of the explosive chamber in the projector system of Hayabusa2 for asteroid sampling

We report a chemical assessment of the explosive chamber in the projector system used during the sampling operation of the Hayabusa2 project at the surface of the C-type asteroid Ryugu. Although the explosion process was designed as a closed system, volatile combustion gases and semivolatile organics were produced together with quenched carbonaceous product. The chemical compositions of the gases, organics, and inorganics were investigated in the screening analysis. A solid-phase microextraction technique and thermal desorption coupled with gas chromatography/mass spectrometry analysis revealed that aliphatic (< C₂₀n-alkanes) and aromatic (< pyrene) hydrocarbons were produced in the closed chamber system. The aromatic ring compositions of the latter showed a semilogarithmic decrease: one ring > two rings > three rings > four rings, resulting in abiogenic molecular patterns. The most intense inorganic fingerprints were due to potassium (K⁺) and chloride (Cl^–) ions derived from the initial KTB explosive and RK ignition charge. We discuss quality control and quality assurance issues applicable to future sample processes during the Hayabusa2 project.