| Project/Area Number |
05833009
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
惑星科学
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| Research Institution | Osaka University |
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Principal Investigator |
TSUCHIYAMA Akira Fac.Sci., Osaka Univ.Associate Prof., 理学部, 助教授 (90180017)
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| Co-Investigator(Kenkyū-buntansha) |
NAGAI Takaya Fac.Sci., Osaka Univ.Assistant Prof., 理学部, 助手 (20243131)
TAKUBO Hiroshi Fac.Sci., Osaka Univ.Professor, 理学部, 教授 (80029678)
YAMANAKA Takamitsu Fac.Sci., Osaka Univ.Professor, 理学部, 教授 (30011729)
MATSUDA Junichi Fac.Sci., Osaka Univ.Professor, 理学部, 教授 (80107945)
UEDA Chiaki Fac.Sci., Osaka Univ.Lecturer, 理学部, 講師 (50176591)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1994: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1993: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | forsterite / metallic iron / troilite / enstatite / evaporation rates / incongruent evaporation / primordial solar nebula / elemental and isotopic fractionation / 分散蒸発 / 元素同位体分別 / 蒸発 / 硫化鉄 / 元素分別 / カイネティクス |
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| Research Abstract |
Evaporation rates and their evaporation coefficients of important minerals forming terrestrial planets (forsterite, metallic iron, and troilite) were determined by evaporation experiments. Forsterite evaporates congruently, and the evaporation obeys a linear rate law. Its evaporation coefficient showed that the evaporation of forsterite under a H_2-rich atmosphere occurs by mechanism similar to that of free evaporation. From the results, evaporation rates of forsterite in a primordial solar nebula can be estimated. Evaporation of metallic iron also obeys a linear rate law, and its evaporation coefficient is close to unity. Incongruent evaporation of troilite with metallic iron residue obeys a linear rate law due to reaction at the troilite-metallic iron interface as a rate-determining process. From the experimental results together with previous data, evaporation rates of important minerals forming terrestrial planets were complied. Elemental fractionation (Mg/Si and Fe/S) due to evaporation of mineral dust in the primordial solar nebula was discussed based on the complied data. It was suggested that incongruent evaporation of enstatite did not occur but apparent congruent evaporation of enstatite occurred, and thus no Mg/Si fractionation is expected. However, Mg/Si fractionation is possible as long as the dust was amorphous Mg-silicate. Fe/S fractionation was expected due to incongruent evaporation of troilite. A model for isotopic mass fractionation due to evaporation of solids was also constructed based on the evaporation rates of the minerals. The fractionation depends on the evaporation rate, diffusion coefficient in the solid, the size of the solid, and isotopic fractionation factor which is determined from the mass of evaporated molecules. Based on the model, conditions for isotopic mass fractionation found in meteorites were estimated successfully.
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