Magnetic field measurements show that Mars possesses strong crustal magnetic anomalies that formed when the planet had an active dynamo. To investigate the origin of this magnetization, we used localized power spectrum analyses to constrain the equivalent depths of thin magnetic layers in the crust. Using a new martian magnetic field model that incorporates data from both the Mars Atmosphere and Volatile EvolutioN and Mars Global Surveyor missions, we found that the equivalent magnetization depths on Mars vary from the surface to 72 km. In the northern hemisphere the magnetization depths are found to be on average 9 km, whereas in the southern hemisphere the depths are on average 32 km. If these depths are interpreted in terms of a thick magnetic layer, magnetization in the northern lowlands could extend from the surface to about 18 km depth, whereas for the southern highlands the magnetic layer could extend from about 20 km depth to the base of the crust. The strongest magnetic anomalies are, in general, associated with deep source depths. Our results are consistent with the hypothesis where strong primordial magnetic materials of the northern hemisphere were excavated from the Borealis impact basin, leaving only strong deep remanent magnetization in the southern hemisphere.

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来自局部功率谱分析的火星磁化深度

磁场测量表明，火星具有强烈的地壳磁异常，这是在行星有一个活跃的发电机时形成的。为了研究这种磁化的起源，我们使用局部功率谱分析来限制地壳中薄磁层的等效深度。使用新的火星磁场模型，该模型结合了来自火星大气和挥发性演化以及火星全球勘测者任务的数据，我们发现火星上的等效磁化深度从地表到 72 公里不等。在北半球，发现磁化深度平均为 9 公里，而在南半球，磁化深度平均为 32 公里。如果用厚磁层来解释这些深度，北部低地的磁化可能从地表延伸到约 18 公里的深度，而在南部高地，磁层可以从大约 20 公里的深度延伸到地壳底部。通常，最强的磁异常与深源深度有关。我们的研究结果与北半球强原始磁性物质是从 Borealis 撞击盆地中挖掘出来的假设一致，在南半球只留下强烈的深部剩磁。