Collisional sticking of organic grains in the solar nebula

为了确定星际有机物在原太阳星云中的分布，研究有机颗粒的生长，进行了星际有机物模拟加热和碰撞实验。我们发现星际间存在2.1 ~ 3.0 AU的有机颗粒，<2.1 AU的硅酸盐颗粒，以及> ~ 3.0 AU的冰粒。我们还发现，在2.2 AU左右蒸发的气体具有很强的还原性。2.1 ~ 3.0 AU的有机质具有很强的粘性；mm级有机颗粒的黏附阈值速度为5 m/s。这表明了有机颗粒聚集体的快速凝聚，星子的形成甚至是湍流吸积盘的早期阶段。该区域的星子成为无球粒陨石的母体。相比之下，<2.1 AU和>3.0 AU的星子是在被动盘形成时形成的，因为硅酸盐和冰粒没有粘性。小于2.1 AU和小于3.0 AU的星子分别成为普通球粒陨石和碳质球粒陨石的母体。在这些框架下，我们讨论了球粒陨石的氧化还原状态，陨石和行星的氧同位素组成，以及球粒的形成。我们成功地用日心距离解释了陨石和行星之间的各种序列：离太阳的序列是地球、火星、LL、L、H、E、Aubrite、HED、Acapulcoite、uilite、CO、CV、CM、CI。

Heating and collision experiments were performed involving interstellar organic material analogue to determine the distribution of interstellar organic material in the proto solar nebula and to investigate the growth of organic grains. We found that there were interstellar organic grains in 2.1-3.0 AU, silicate grains <2.1 AU, and ice grains>3.0 AU. We also found that gas evaporated at around 2.2 AU is very reductive. The organic material in 2.1-3.0 AU is very sticky ; the sticking threshold velocity of the mm-size organic grains is 5 m/s. This shows a very rapid coagulation of organic grain aggregates, the formation of planetesimals even the early stage of the turbulent accretion disk. The planetesimals in this region become achondrites' parent bodies. In contrast, the formation of planetesimals in <2.1 AU and >3.0 AU occur when passive disk is formed, because silicate and ice grains are not sticky. The planetesimals in <2.1 AU and >3.0 AU become ordinary and carbonaceous chondrites' parent bodies, respectively. In these framework, we discuss a redox state of chondrites, an oxygen isotope composition of meteorites and planets, and the formation of chondrules. We have succeded to give an explanation for various sequences among meteorites and planets by the heliocentric distance only : the sequence from the sun is the Earth, Mars, LL, L, H, E, Aubrite, HED, Acapulcoite, Ureilite, CO, CV, CM, CI.