同位素的证据表明,同时形成了圆柱体和耐火性内含物
Martin Bizzarro1, Joel A Baker, Henning Haack
1Danish Lithosphere Centre, Øster Voldgade 10, Denmark. mbi@dlc.ku.dk
Nature
|September 17, 2004
概括
原始的石揭示了太阳系早期的形成. 富含和的含有物 (CAI) 和圆柱体同时形成,挑战了这些古老的太阳系材料之前的时间表.
科学领域:
- 太空化学 太空化学
- 行星科学 行星科学
- 太阳系早期的进化过程
背景情况:
- 原始的石 (石) 保存了早期太阳系的积累盘的记录.
- 富含和的含 (CAI) 和孔德鲁是最古老的材料之一,是通过热处理星云固体形成的.
- 现有的模型表明,chondrules是在CAI数百万年后形成的,这与粒子动态不一致的时间尺度.
研究的目的:
- 通过同位素分析研究CAI和chondrules的形成时间表.
- 为了使这些原始太阳系天体的形成时间表与动态约束相协调.
主要方法:
- 分析过多的-26 (26Mg) 由短寿命-26 (26Al) 在CAI和来自阿伦德石的体中衰变而产生的过多-26.
- 使用26Al-26Mg系统进行放射测年,以确定初始的26Al/27Al比率和模型年龄.
主要成果:
- 六个CAI产生了一个同位素,表明最初的26Al/27Al比率为 (5.25 ± 0.10) x 10−5,模型年龄精确为±30,000年.
- 这些CAI表明形成的时间非常短,约为5万年.
- 宏德鲁尔表现出最初26Al/27Al比率的范围,从 (5.66 ± 0.80) x 10−5到 (1.36 ± 0.52) x 10−5,表明与CAI同时形成并持续至少1.4亿年.
结论:
- 阿连德柱的形成与CAI的形成同时开始,而不是像以前认为的那样几百万年后.
- 在年轻的太阳系中,体形成过程可能至少持续了1.4亿年,可能是2-3亿年.
- 这些发现需要对早期太阳系的热和动态演变进行修订模型.
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