The physics and chemistry of solar nebula shock waves: Applications to chondrule formation

摘要

Chondrules are a major component of primitive meteorites and are thought to be among the first solids to have formed in the solar system. However, the circumstances around the formation of chondrules have remained a mystery for the 200 years that chondrules have been known to exist. In this work, a model is developed to show that shock waves in the nebula could have been responsible for the complex thermal processing that chondrules are thought to have experienced. By studying different sizes of shock waves, it is shown that for shock waves to have been the dominant chondrule producing mechanism in the nebula, the shocks would have to be large (>1000 km) in size. Such shocks may be linked to the formation or evolution of Jupiter within the solar nebula. In addition, the thermal evolution of chondrules by shock waves can explain the geometric properties of compound chondrules if these objects formed by the collisions of molten chondrules. Finally, for the first time, the case of a shock wave passing through an icy region of the solar nebula is studied. It is found that such a situation may have produced conditions that would allow silicates to be hydrated on very short time scales, explaining the presence of phyllosilicates in the accretionary rims around chondrules in CM chondrites.