日本地球惑星科学連合2018年大会

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[JJ] ポスター発表

セッション記号 P (宇宙惑星科学) » P-PS 惑星科学

[P-PS09] 宇宙における物質の形成と進化

2018年5月22日(火) 10:45 〜 12:15 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:橘 省吾(東京大学大学院理学系研究科宇宙惑星科学機構)、三浦 均(名古屋市立大学大学院システム自然科学研究科)、野村 英子(東京工業大学理学院地球惑星科学系、共同)、大坪 貴文(宇宙航空研究開発機構 宇宙科学研究所)

[PPS09-P03] 17P/Holmes彗星の中間赤外線スペクトルから探る鉱物の形成環境

*新中 善晴1,3大坪 貴文2河北 秀世3本田 充彦4渡部 潤一1 (1.大学共同利用機関法人 自然科学研究機構 国立天文台、2.JAXA/ISAS、3.京都産業大学、4.久留米大学)

キーワード:彗星、17P/Holmes、中間赤外線スペクトル、鉱物組成比

Dust grains of crystalline silicate, which is rarely presented in an interstellar space, were found in cometary nuclei (Messenger et al. 1996, LPI, 27, 867; Wooden et al. 1999, ApJ, 517, 1058, references therein). It is thought that these crystalline silicates had formed by annealing or condensations of amorphous grains near the Sun in the solar nebula, and incorporated into a cometary nucleus in a cold region (farther than formation regions of the crystalline silicates) by radial transportation in the solar nebula. It is considered that transportation mechanisms to outside of the solar nebula were turbulent and/or X-wind. An abundance of the crystalline dust grains was therefore expected to be smaller as far from the Sun (Gail, 2001, A&A, 378, 192; Bockelée-Morvan et al. 2002, A&A, 384, 1107). Namely, the abundance ratio of the crystalline silicate in cometary dust grains relates a degree of mass transportation and a distance from the Sun when cometary nucleus formed in the Solar nebula.

The mass ratio of crystalline silicates of dust grains is determined from by Si-O stretching vibrational bands of silicate grains around 10 μm using the difference of spectral band features between crystalline and amorphous grains. We present the crystalline-to-amorphous mass ratio of silicate grains in the comet 17P/Holmes by using the thermal emission mode of the dust grains (Ootsubo et al. 2007, P&SS, 55, 1044) applied to the mid-infrared spectra of the comet. These spectra were taken by the COMICS mounted on the Subaru Telescope on 2007 October 25, 26, 27 and 28 immediately after the great outburst of the comet (started on October 23). We discuss about formation condition of minerals incorporated into the nucleus of the comet based on the derived mass ratio of silicate grains of the comet.