Nebular shock waves generated by planetesimals passing through Jovian resonances: Possible sites for chondrule formation
Nebular shock waves generated by planetesimals passing through Jovian resonances: Possible sites for chondrule formation
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星子穿过木星共振产生的星云冲击波：球粒形成的可能地点
DOI：
10.1111/j.1945-5100.2009.tb00736.x
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发表时间：
2009
影响因子：
2.2
通讯作者：
S. Weidenschilling
中科院分区：
文献类型：
--
作者：
L. Hood;F. Ciesla;N. Artemieva;F. Marzari;S. Weidenschilling
原始小行星带包含至少几百个，可能多达10，000个直径为1000公里或更大的天体。在木星形成后，星云的气体阻力加上这些天体通过木星共振的通道，产生了高偏心率（e = 0.3 - 0.5），低倾角（i < 0.5°），因此，相对于星云气体和非共振星子，“共振”天体的速度很高（3-10 km/s）。这些高速将通过两种机制在星云气体中产生冲击波。首先，弓形激波是由共振天体相对于星云的超音速运动产生的。其次，共振体与非共振体的高速碰撞会在碰撞点附近产生撞击蒸气羽流冲击。这两种类型的冲击都足以熔化星云中的球粒前体，并且都与CAIs和大多数球粒形成之间的时间延迟为100万年至150万年的同位素证据相一致。在这里，最初的模拟首次报道的冲击波产生的星云和当地的星云体积，将处理这些冲击作为一个函数的冲击大小和相对速度。其次，近似的最大球粒质量生产的弓冲击和冲击产生的冲击，假设一个简化的星子人口和向内迁移到共振的速度与以前的模拟一致的估计。基于这些最初的一阶计算，撞击产生的冲击只能解释原始小行星带中陨石球粒最小可能质量（1024 - 1025 g）的一小部分。然而，弓形激波可能是球粒产生的更有效的来源，可以解释估计的最小球粒质量的10-100倍。
Abstract— The primordial asteroid belt contained at least several hundred and possibly as many as 10,000 bodies with diameters of 1000 km or larger. Following the formation of Jupiter, nebular gas drag combined with passage of such bodies through Jovian resonances produced high eccentricities (e = 0.3‐0.5), low inclinations (i < 0.5°), and, therefore, high velocities (3–10 km/s) for “resonant” bodies relative to both nebular gas and non‐resonant planetesimals. These high velocities would have produced shock waves in the nebular gas through two mechanisms. First, bow shocks would be produced by supersonic motion of resonant bodies relative to the nebula. Second, high‐velocity collisions of resonant bodies with non‐resonant bodies would have generated impact vapor plume shocks near the collision sites. Both types of shocks would be sufficient to melt chondrule precursors in the nebula, and both are consistent with isotopic evidence for a time delay of ˜1‐1.5 Myr between the formation of CAIs and most chondrules. Here, initial simulations are first reported of impact shock wave generation in the nebula and of the local nebular volumes that would be processed by these shocks as a function of impactor size and relative velocity. Second, the approximate maximum chondrule mass production is estimated for both bow shocks and impact‐generated shocks assuming a simplified planetesimal population and a rate of inward migration into resonances consistent with previous simulations. Based on these initial first‐order calculations, impact‐generated shocks can explain only a small fraction of the minimum likely mass of chondrules in the primordial asteroid belt (˜1024‐1025g). However, bow shocks are potentially a more efficient source of chondrule production and can explain up to 10–100 times the estimated minimum chondrule mass.