@inproceedings{oai:jaxa.repo.nii.ac.jp:00020661,
 author = {中本, 泰史 and 木多, 紀子 and 橘, 省吾 and Nakamoto, Taishi and Kita, Noriko T. and Tachibana, Shogo},
 book = {第36回月・惑星シンポジウム, Proceedings of the 36th ISAS Lunar and Planetary Symposium},
 month = {Nov},
 note = {Chondrules are major components in primitive meteorites and consist of 70 percent by volume in ordinary chondrites. They are considered to be formed by a flash heating of dusts in the protoplanetary disk, though the nature of the heating mechanism is not yet well understood. In order to evaluate some basic factors in the heating mechanism of chondrule formation, examined were the rate of chondrule precursor heating and its time variation that explain the abundance and the observed age distribution of chondrules. The literature data of Al-26 ages of chondrules from the least equilibrated ordinary chondrites (LL3.0 to 3.1) was compiled, that range from 1 Myr to 3 Myr with a peak at about 1.8 Myr relative to the formation time of the oldest CAIs. Making a simple phenomenological model for chondrule formation, the total amount of heating, the fraction of reheated chondrules, and the evolution of the rate of chondrule precursor heating were evaluated. The model considers that the each event heated only a small fraction of existed dust material in the chondrule forming region at one time and numerous heating events produced a huge amount of chondrules. The result indicates that an average number of heating events experienced by a dust particle should be 1.2 times or higher and more than a half of the present chondrules were reheated. To explain observed chondrule age distributions, the chondrules formation started sometime between 0.6 to 1.3 Myr after the CAI formation and ended at 2.2 to 2.3 Myr. The rate of chondrule precursor heating has a peak at 0.3 to 0.6 Myr earlier than that of the observed age distribution of chondrules. The present calculation indicates that the starting time of the chondrule formation epoch is not zero. Thus, it is proposed that the heating events responsible for the chondrule formation could be different from that for CAI formation., 資料番号: AA0046650012},
 pages = {45--48},
 publisher = {宇宙航空研究開発機構宇宙科学研究本部, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA/ISAS)},
 title = {History of chondrule forming heating events inferred from chondrule age distribution},
 year = {2003}
}