Timing of the martian dynamo: New constraints for a core field 4.5 and 3.7 Ga ago
Timing of the martian dynamo: New constraints for a core field 4.5 and 3.7 Ga ago
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DOI：
10.1126/sciadv.aba0513
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发表时间：
2020-05
期刊：
影响因子：
13.6
通讯作者：
A. Mittelholz;C. L. Johnson;C. L. Johnson;Joshua M. Feinberg;Benoit Langlais;Roger J. Phillips
中科院分区：
文献类型：
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作者：
A. Mittelholz;C. L. Johnson;C. L. Johnson;Joshua M. Feinberg;Benoit Langlais;Roger J. Phillips
MAVEN磁场数据表明，在4.5和3.7Ga之前，火星的发电机磁场是活跃的。火星盆地Hellas、Argyre和Isidis上方没有地壳磁场通常被解释为41亿年前的早期发电机的证据，或3.9亿年前之后的晚期发电机的证据。我们使用新的MAVEN磁场数据重新审视了这些解释。4.5Ga古老的北冰洋盆地上存在弱场，向与盆地边缘相关的强场过渡。在3.7Ga的旧Lucus Planum上方，也可以探测到局限于近地表的磁场。我们的结论是，在希腊、乌托邦、阿盖尔和伊西迪斯盆地形成之前和之后都存在发电机。如果撞击挖掘出很大一部分强磁性地壳，并暴露出磁性矿物浓度较低的更深层次的物质，那么长寿命的类地球发电机与大型盆地内没有磁化是一致的。
MAVEN magnetic field data indicate that a martian dynamo field was active 4.5 and 3.7 Ga ago. The absence of crustal magnetic fields above the martian basins Hellas, Argyre, and Isidis is often interpreted as proof of an early, before 4.1 billion years (Ga) ago, or late, after 3.9 Ga ago, dynamo. We revisit these interpretations using new MAVEN magnetic field data. Weak fields are present over the 4.5-Ga old Borealis basin, with the transition to strong fields correlated with the basin edge. Magnetic fields, confined to a near-surface layer, are also detected above the 3.7-Ga old Lucus Planum. We conclude that a dynamo was present both before and after the formation of the basins Hellas, Utopia, Argyre, and Isidis. A long-lived, Earth-like dynamo is consistent with the absence of magnetization within large basins if the impacts excavated large portions of strongly magnetic crust and exposed deeper material with lower concentrations of magnetic minerals.