最近,火星上高度地区由不稳定的赤道冰在低斜度期间升华而形成的富含冰的沉积物
Benjamin Levrard1, François Forget, Franck Montmessin
1Astronomie et Systèmes Dynamiques, IMC-CNRS UMR8028, 77 Avenue Denfert-Rochereau, 75014 Paris, France. blevrard@imcce.fr
Nature
|October 29, 2004
概括
在火星的高度上存在着近地表面的巨大冰库,其度高达100%. 这些沉积物可能是在低斜度时期通过直接冰沉积形成的,由赤道冰的升华驱动.
科学领域:
- 行星科学 行星科学
- 天文地质学 天文地质学
- 气候科学 气候科学
背景情况:
- 火星奥德赛号的马射线光谱仪数据表明,在火星的高度处,表面附近有大量的冰.
- 形态学证据显示,厚厚的,分层的,富含冰的沉积物和危冰的特征仅在高度地区.
- 以前涉及大气水交换或极地冰运输的模型难以解释观察到的冰度.
研究的目的:
- 提出和验证一个新的模型,用于高度火星冰沉积物的形成.
- 为了解释在特定的火星地区观察到的高度的水冰.
- 为了将冰沉积物形成与火星在地质时间尺度上的斜率变化联系起来.
主要方法:
- 分析来自火星奥德赛的马射线光谱仪数据.
- 检查层状冰沉积物和危冰特征的形态证据.
- 利用全球气候模型模拟来估计冰的积累率.
- 研究火星倾斜周期在冰的再分配中的作用.
主要成果:
- 冰的度从60°度的70%到极点附近的100%不等,通常覆盖着薄薄的,没有冰的材料.
- 提出了一种新的机制:在低斜度 (<25°) 期间,在高度地区直接沉积冰.
- 这个过程涉及从之前的高斜度游览中形成的赤道冰库中升华.
结论:
- 在过去的1000万年里,火星的斜率变化是形成厚厚的,沉积的,分层的冰沉积物的关键驱动因素.
- 拟议的模型成功地解释了火星高度的近地冰的分布和度.
- 这种机制为观测到的巨大的冰库提供了比以前的模型更强大的解释.
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