Although Mars does not possess a global magnetic field today, regions of its crust are strongly magnetized, consistent with an early dynamo, likely powered by rapid heat flow from the core. If the core is undergoing crystallization, the associated compositional changes would provide an additional mechanism for driving convection—probably the dominant driver for Earth's dynamo today. This raises the question: does the lack of a global dynamo field on Mars suggest the absence of a partially crystallized core? More generally, what is the range of possibilities for the history and future of the Martian dynamo and which scenarios could be ruled out by the presence or absence of a solid inner core? Here we develop a new internal structure, thermal evolution, and buoyancy flux model to investigate the conditions under which the Martian core could experience compositionally driven convection, either in the past or the future. We show that the presence of a partially crystallized core is compatible with the lack of a dynamo today but that such a scenario implies the Martian dynamo could reactivate at some point in the future. We find that top‐down core crystallization (iron snow) requires weak light element partitioning, introduces limited buoyancy flux, and is unlikely to be effective at driving convection. Our model demonstrates how sulfur content & partitioning and core conductivity & expansivity determine which dynamo regimes are possible, can help in assessing implications of future observations relating to the Martian core, and forms the basis for further comparative study across rocky planets.

中文翻译：

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火星发电机的历史和未来以及假想固体核心的含义

尽管火星今天没有全局磁场，但其表壳的区域被强烈磁化，这与早期的发电机一致，这很可能是由来自岩心的快速热流推动的。如果核心正在结晶，则相关的成分变化将提供驱动对流的其他机制-可能是当今地球发电机的主要驱动因素。这就提出了一个问题：火星上缺乏全球性的发电机场是否表明不存在部分结晶的岩心？更普遍地讲，火星发电机的历史和未来的可能性范围是什么，可以通过存在或不存在坚实的内在核心来排除哪些情况？在这里，我们开发了一种新的内部结构，即热演化，和浮力通量模型来研究火星岩心在过去或将来可能经历成分驱动的对流的条件。我们表明，部分结晶的核的存在与当今缺乏发电机兼容，但这种情况暗示火星发电机可能在将来的某个时候重新激活。我们发现，自上而下的岩心结晶（铁雪）要求弱的轻元素分配，有限的浮力通量，并且不太可能有效地促进对流。我们的模型演示了硫含量和分区以及岩心电导率和膨胀率如何确定可能的发电机形式，可以帮助评估与火星岩心有关的未来观测结果的含义，