PLANETESIMAL COLLISIONS AS A CHONDRULE FORMING EVENT
PLANETESIMAL COLLISIONS AS A CHONDRULE FORMING EVENT
复制标题
星子碰撞作为球粒形成事件
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
Y. Hasegawa
中科院分区：
文献类型：
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作者：
S. Wakita;Yuji Matsumoto;S. Oshino;Y. Hasegawa
球粒陨石含有独特的球状物质，名为球粒陨石：在太阳星云的高温条件下熔化的亚毫米大小的硅酸盐颗粒。我们用数值方法研究了球粒形成过程中的一个过程--行星小碰撞。以前的研究发现，当撞击速度超过2.5kM S−1时，通过原行星-行星微小碰撞产生的撞击喷流可以以撞击器质量的1%形成球粒。根据球粒的矿物学数据，未分化的行星体比潜在的分化的原始行星更适合形成球粒碰撞。我们使用激波物理代码检查小行星-小行星碰撞，发现两件事：一是小行星-小行星碰撞产生的球粒数量几乎与原行星-小行星碰撞相同(∼为1%)。二是当两颗行星相互碰撞时，球粒陨石的产生量随着撞击速度的增加而增大。我们还发现，球粒陨石的祖先可能起源于大目标(行星体或原行星)比小撞击体(行星体)更深的区域。因此，目标的组成对于充分解释目前采样的球粒陨石的矿物学数据是重要的。
Chondritic meteorites contain unique spherical materials named chondrules: sub-mm sized silicate grains once melted in a high temperature condition in the solar nebula. We numerically explore one of the chondrule forming processes—planetesimal collisions. Previous studies have found that impact jetting via protoplanet–planetesimal collisions can make chondrules with 1% of the impactors’ mass, when the impact velocity exceeds 2.5 km s−1. Based on the mineralogical data of chondrules, undifferentiated planetesimals would be more suitable for chondrule-forming collisions than potentially differentiated protoplanets. We examine planetesimal–planetesimal collisions using a shock physics code and find two things: one is that planetesimal–planetesimal collisions produce nearly the same amount of chondrules as protoplanet–planetesimal collisions (∼1%). The other is that the amount of produced chondrules becomes larger as the impact velocity increases when two planetesimals collide with each other. We also find that progenitors of chondrules can originate from deeper regions of large targets (planetesimals or protoplanets) than small impactors (planetesimals). The composition of targets is therefore important, to fully account for the mineralogical data of currently sampled chondrules.