The fate of early Mars' lost water: The role of serpentinization
The fate of early Mars' lost water: The role of serpentinization
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DOI：
10.1002/jgre.20089
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发表时间：
2013-05-01
影响因子：
4.8
通讯作者：
Leblanc, Francois
中科院分区：
文献类型：
--
作者：
Chassefiere, Eric;Langlais, Benoit;Leblanc, Francois
早期火星上存在的水的命运仍然是个谜。我们提出了一个简单的模型的基础上蛇纹石化，热液蚀变过程，可能会产生磁铁矿和储存水。我们的模型调用蛇纹岩化在大约5亿至8亿年，而发电机是活跃的，这可能已经继续形成后的地壳二分法。我们表明，目前的磁场测量火星全球勘测者在南半球是一致的，类似的500米厚的全球等效层（GEL）的水被困在蛇纹岩。蛇纹化导致H-2的释放。释放的H原子通过热逃逸损失到空间，增加了与大气交换的水库中的D/H比。我们指出，在目前的大气中的D/H比的值（类似于5）也是一致的蛇纹石化的一个类似500米厚的水凝胶。我们重新评估了非热逃逸在从地球上移除水方面的作用。通过考虑一个更新的太阳风电离层相互作用表示，我们表明，氧逃逸的H同位素分馏的贡献是可以忽略不计的。我们的研究结果表明，大量的水（高达类似330- 1030米厚的凝胶）存在于表面在诺亚纪，类似于从山谷网络的形态分析推断的数量，今天可以存储在地下蛇纹岩。
The fate of water which was present on early Mars remains enigmatic. We propose a simple model based on serpentinization, a hydrothermal alteration process which may produce magnetite and store water. Our model invokes serpentinization during about 500 to 800Myr, while a dynamo is active, which may have continued after the formation of the crustal dichotomy. We show that the present magnetic field measured by Mars Global Surveyor in the southern hemisphere is consistent with a similar to 500m thick Global Equivalent Layer (GEL) of water trapped in serpentine. Serpentinization results in the release of H-2. The released H atoms are lost to space through thermal escape, increasing the D/H ratio in water reservoirs exchanging with atmosphere. We show that the value of the D/H ratio in the present atmosphere (similar to 5) is also consistent with the serpentinization of a similar to 500m thick water GEL. We reassess the role of nonthermal escape in removing water from the planet. By considering an updated solar wind-ionosphere interaction representation, we show that the contribution of oxygen escape to H isotopic fractionation is negligible. Our results suggest that significant amounts of water (up to a similar to 330-1030m thick GEL) present at the surface during the Noachian, similar to the quantity inferred from the morphological analysis of valley networks, could be stored today in subsurface serpentine.