撞击起源对火星半球二分法的影响
F Nimmo1, S D Hart, D G Korycansky
1Department of Earth and Planetary Sciences, University of California, Santa Cruz, 1156 High Street, Santa Cruz, California 95064, USA. fnimmo@es.ucsc.edu
Nature
|June 27, 2008
概括
巨大的撞击可能解释了火星的半球二分法,创造了一个较低的地和较薄的地. 这种影响模型还解释了反极地磁场下降和北方低地地地融的起源.
科学领域:
- 行星科学 行星科学
- 地质物理学 地质物理学
- 冲击石坑的形成
背景情况:
- 火星半球二分法,以半球之间对比的地厚度和高度为特征,仍然是一个长期存在的行星科学.
- 对于二分法形成的现有假设包括内部过程,如对流或外部因素,如巨大的冲击.
研究的目的:
- 量化测试火星半球二分论的巨大撞击假说.
- 为了调查一个单一的撞击事件是否可以解释火星二分法的多个观察到的特征.
主要方法:
- 利用一个高分辨率的,二维的,轴对称的水解码来模拟火星早期的垂直冲击.
- 模拟了一系列与火星地质历史相关的冲击参数.
主要成果:
- 撞击模型成功地挖出了与观察到的二分法相一致的地腔.
- 撞击反极点上的地破坏与观察到的磁场强度下降有关.
- 预计北方低地撞击产生的融化源自一个深层,枯竭的地幔源.
结论:
- 一个巨大的撞击事件为火星半球二分法提供了一个可行的解释.
- 撞击模型与对立磁场异常的观测以及火星石 (shergottites) 的组成一致.
- 据估计,二分法形成发生在火星积累后大约1亿年.
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