Hf-W-Th证据证明火星的快速增长及其作为行星胚胎的地位
1Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637, USA. dauphas@uchicago.edu
Nature
|May 27, 2011
概括
火星经历了快速增长,在180万年内达到其一半大小. 这支持了火星作为一个浅的行星胚胎的理论,在太阳系早期形成期间避免了碰撞.
科学领域:
- 行星科学 行星科学
- 太空化学 太空化学
- 地质物理学 地质物理学
背景情况:
- 地球行星形成模型难以解释火星的小尺寸,与地球和金星不同.
- 以前对火星积累时间尺度的估计,对于理解它的起源至关重要,由于火星地幔的/ (Hf/W) 比率的不确定性而受到很小的限制.
- 火星的现有积累时间尺度范围广泛,从0到1500万年 (Myr).
研究的目的:
- 为了准确确定火星的积累时间表和Hf/W比率.
- 为了测试火星是行星胚胎,逃脱了增殖的假设.
- 改进地球行星形成和太阳系早期演变的模型.
主要方法:
- 在雪戈提特,纳克莱特和查西尼特石中利用了哈夫-182 (182Hf) -182 (182W) 衰变系统.
- 确立了/哈夫 (Th/Hf) 和哈夫-176/哈夫-177 (176Hf/177Hf) 的比率之间的相关性,以纠正母体过程.
- 使用已建立的相关性计算了火星地幔的精确Hf/W比.
主要成果:
- 火星迅速增长,在1.8亿年或更短的时间内达到目前大小的一半左右.
- 确定火星地幔的精确Hf/W比为3.51±0.45.
- 这种快速增长与火星是一个浅的行星胚胎相一致.
结论:
- 火星的快速增长发生在太阳系历史的早期,在星云气体消散之前.
- 这些发现支持火星形成的"浅胚胎"假设.
- 早期的积聚允许建立一个岩海洋,可能由-26 (26Al) 衰变提供动力.
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