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

[PCG21-P05] Heating experiments of GEMS simulants

*Marina Hagiwara¹, Aki Takigawa¹, Shogo Tachibana¹ (1.The University of Tokyo)

Keywords:material evolution in space, GEMS, crystallization

Glass embedded with metals and sulfides (GEMS), found as the main component of anhydrous chondritic-porous interplanetary dust particles (CP-IDPs, thought to be originated from comets), is known as the most primitive material which formed the Solar System [1]. In addition to this amorphous silicate, it is suggested observationally that comets, formed in the outer region of the Solar System, include crystalline silicates [2]. Therefore, it has been considered that comets were formed by the contribution of both the cold materials from the outer region of the solar nebula and the hot materials transported from the inner region [1]. Although the origin of GEMS is controversial [3], the recent experiment raised the possibility that GEMS have condensed by quenching from dense gas in the inner region of the Solar System [3]. In this case, GEMS may have experienced crystallization to some extent by heating before being transported to the outer region. In this study, the heating experiments of S-free GEMS-like materials (amorphous silicates with Fe metal core) [4] were conducted to observe the crystallization of the samples and verify whether the infrared spectroscopic observation of cometary dusts could be explained by the features of heated GEMS simulants. At each experiment, the sample in the gold-mirror furnace [5] was heated under vacuum (~ 10^-4 Pa) by 20℃/min until reaching the heating temperature (620, 720, 820, and 920℃), and then kept at the temperature for certain duration (0.5-72 h). Starting material and heated samples were analyzed by XRD (Rigaku MiniFlex-600C) and FT-IR (JASCO FT/IR-4200). From the analyses so far, olivine and a small amount of pyroxene crystallized from the samples, and the compositional changes in olivine and kamacite also observed in much heated samples. In addition, the infrared spectral features of the heated samples could explain qualitatively the observation of cometary dusts. Furthermore, magnesium numbers of crystallized olivine are focused to discuss the quantitative change of their values by heating conditions.

[1] Keller, L. P. and Messenger, S. (2011) GCA 75, 5336.
[2] Brucato, J. R. (1999) A&A 348, 1012.
[3] Kim, T. H. et al. (2021) A&A 656, A42.
[4] Enomoto, H. and Takigawa, A. (2023) LPSC LVI #1376.
[5] Yamamoto, D. and Tachibana, S. (2018) ACS Earth Space Chem. 2, 778.