[P-CG21] Origin and evolution of materials in space

[PCG21-P04] Experimental investigation of sublimation products of forsterite

*Shiori Inada¹, Atsuki Ishibashi¹, Shogo Tachibana¹, Tetsuya Hama¹ (1.the University of Tokyo)

Keywords:sublimation, evaporation, dust, planetary materials, forsterite

Sublimation or evaporation of dust is likely to be a major process during star and planetary system formation, which results in chemical diversity of rocky planetary materials. This is suggested from a wide variety of Solar System materials exhibiting properties attributed to sublimation/evaporation that they underwent in the past [1,2]. Motivated by this cosmochemical importance, a lot of basic experimental studies have been conducted on the sublimation/evaporation of substances constituting meteorites and planets such as silicate, oxide, sulfide, and metallic minerals and melts [3,4]. However, the understanding of their physicochemical elementary processes is still limited. This is particularly evident from the fact that they cannot even be expressed as chemical reaction formula in most cases because the gas species produced through the decomposition concurrent with the sublimation/evaporation are not clarified. In the previous experiments aiming to interpret extraterrestrial solid samples, the gas-phase sublimation/evaporation products attracted less attention than the condensed-phase residues. On the other hand, the gas products are recently drawing greater interest because of the increasing number of detections of refractory molecules in star- and planetary system-forming regions using the Atacama Large Millimeter/submillimeter Array (ALMA), which are potentially related to sublimation/evaporation of dust [5-7]. The clarification of the sublimation/evaporation products is thus becoming more important as the first step to understand these astronomical observations from the chemical perspective and relate them to the cosmochemical studies.

To experimentally approach this problem, we recently developed a new ultra-high vacuum apparatus consisting of a resistive heating system and a quadrupole mass spectrometer. Using this apparatus, we can heat samples at controlled temperatures from 673 to ~2000 K and detect the sublimated/evaporated nascent products (atoms and molecules) under collision-free conditions. We first targeted sublimation of forsterite (Mg₂SiO₄), which is a major mineral constituting primitive meteorites and is likely to be present in star-forming regions as dust [8]. The preliminary results will be presented in this presentation.

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