Chondrule formation in particle-rich nebular regions at least hundreds of kilometres across
Chondrule formation in particle-rich nebular regions at least hundreds of kilometres across
复制标题
直径至少数百公里的富含粒子的星云区域形成球粒
作者：
J. Cuzzi;C. Alexander
球粒是毫米大小的小球（主要是硅酸盐），主导着原始陨石的纹理。它们的形成机制是有争议的，但它们的绝对丰度表明这种机制在早期的内太阳系中既充满活力又无处不在。这些过程，如冲击波，太阳耀斑或星云闪电，在不同的长度尺度上运作，很难与球粒的性质直接联系起来。球粒中的挥发性元素已经耗尽，但令人惊讶的是，它们几乎没有显示出人们所期望的较轻同位素的相关损失的证据。在这里，我们报告了一个模型，其中熔融的球粒与其他球粒蒸发的气体达到平衡，并以自然的方式解释了观测结果。陨石球粒形成的区域半径必须大于150- 6，000公里，并且必须具有至少10 m-3的先驱数密度。这些限制可能排除了星云闪电，也使远离星云中平面的形成成为问题。球粒组成的广泛范围可能是当地前体浓度和当地丰富的水冰或蒸汽的不同组合的结果。
Chondrules are millimetre-sized spherules (mostly silicate) that dominate the texture of primitive meteorites. Their formation mechanism is debated, but their sheer abundance suggests that the mechanism was both energetic and ubiquitous in the early inner Solar System. The processes suggested—such as shock waves, solar flares or nebula lightning—operate on different length scales that have been hard to relate directly to chondrule properties. Chondrules are depleted in volatile elements, but surprisingly they show little evidence for the associated loss of lighter isotopes one would expect. Here we report a model in which molten chondrules come to equilibrium with the gas that was evaporated from other chondrules, and which explains the observations in a natural way. The regions within which the chondrules formed must have been larger than 150–6,000 km in radius, and must have had a precursor number density of at least 10 m-3. These constraints probably exclude nebula lightning, and also make formation far from the nebula midplane problematic. The wide range of chondrule compositions may be the result of different combinations of the local concentrations of precursors and the local abundance of water ice or vapour.
影响因子：
3.2
作者：
V. Mannings;A. Boss;S. Russell
通讯作者：
V. Mannings;A. Boss;S. Russell