同位素对地球积累的限制
Isaac J Onyett1, Martin Schiller2, Georgy V Makhatadze2
1Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Copenhagen, Denmark. isaac.onyett@sund.ku.dk.
Nature
|June 14, 2023
概括
原始的石不是地球上的构建块. 相反,早期形成的分化小行星是行星的关键组成部分,同位素的变化跟踪了行星形成期间内外太阳系材料的混合.
科学领域:
- 星球科学
- 宇宙化学
- 同位素地化学
背景情况:
- 了解地球行星的形成需要对前体材料的了解.
- 岩石体中的核合成变异可以追踪行星的构建块.
- 同位素 (Si) 是耐火元素的关键标记物.
研究的目的:
- 在石中确定的核合成成分 (μ30Si).
- 为了确定陆地行星的前体材料.
- 为了重建内部太阳系的积累历史.
主要方法:
- 在原始和差异化石中分析同位素组成 (μ30Si).
- 内部和外部太阳系天体之间的Si值的比较.
- 30Si值与积累年龄和其他同位素标记物 (Mo,Zr,Ni) 的相关性.
主要成果:
- 内部太阳系的天体 (包括火星) 显示出μ30Si的缺陷,而体则显示出μ30Si的过剩.
- 体不是主要的构建块;差异化小行星材料是主要组成部分.
- 地球的前体含有~26%的Si-丰富的外太阳系物质,而火星的形成较早,避免了这种丰富.
- 火星和原地球的Si组成与通过碰撞生长和石积累的快速形成 (<300万年) 一致.
- 地球的同位素组成与石积聚模型一致,考虑到波动性和月球形成的影响.
结论:
- 地球行星的形成涉及不同的内部和外部太阳系材料的混合.
- 早期形成的分化小行星,而不是体,是陆地行星的重要组成部分.
- 快速积聚模型解释了火星和地球的同位素特征,强调了石积聚的作用.
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