Paleomagnetic Evidence of a Low-Temperature Origin of Carbonate in the Martian Meteorite ALH84001
Paleomagnetic Evidence of a Low-Temperature Origin of Carbonate in the Martian Meteorite ALH84001
复制标题
火星陨石 ALH84001 中碳酸盐低温成因的古地磁证据
DOI：
10.1126/science.275.5306.1629
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发表时间：
1997
期刊：
影响因子：
56.9
通讯作者：
H. Vali
中科院分区：
文献类型：
--
作者：
J. Kirschvink;A. Maine;H. Vali
火星上存在生命的间接证据来自对ALH 84001陨石的研究。碳酸盐的形成温度是有争议的;一些估计认为20° C至80°C，而另一些则超过650°C。古地磁学可以用来区分这些可能性，因为加热可以使亚铁磁性矿物重新磁化。对来自ALH 84001破碎区的两个相邻辉石颗粒的研究表明，每个颗粒都具有稳定的自然剩磁（NRM），这意味着当颗粒冷却时，火星具有相当大的磁场。然而，来自这些粒子的NRM方向不同，这意味着陨石自从大约40亿年前内部破碎区形成以来没有被显著加热。碳酸盐球的形成时间晚于角砾岩作用，因此形成于低温下。
Indirect evidence for life on Mars has been reported from the study of meteorite ALH84001. The formation temperature of the carbonates is controversial; some estimates suggest 20° to 80°C, whereas others exceed 650°C. Paleomagnetism can be used to distinguish between these possibilities because heating can remagnetize ferrimagnetic minerals. Study of two adjacent pyroxene grains from the crushed zone of ALH84001 shows that each possesses a stable natural remanent magnetization (NRM), implying that Mars had a substantial magnetic field when the grains cooled. However, NRM directions from these particles differ, implying that the meteorite has not been heated significantly since the formation of the internal crushed zone about 4 billion years ago. The carbonate globules postdate this brecciation, and thus formed at low temperatures.