| Abstrakt: |
The terrestrial planetary bodies display a wide variety of surface expressions and histories of volcanic and tectonic, and magnetic activity, even those planets with apparently similar dominant modes of heat transport (e.g., conductive on Mercury, the Moon, and Mars). Each body also experienced differentiation in its earliest evolution, which may have led to density‐stabilized layering in its mantle and a heterogenous distribution of heat‐producing elements (HPE). We explore the hypothesis that mantle structure exerts an important control on the occurrence and timing of geological processes such as volcanism and tectonism. We numerically investigate the behavior of an idealized model of a planetary body where HPE are assumed to be sequestered in a stabilized layer at the top or bottom of the mantle. We find that the mantle structure alters the patterns of heat flow at the boundaries of major heat reservoirs: The mantle and core. This modulates the way in which heat production influences geological processes. In the model, the mantle structure is a dominant control on the relative timing of fundamental processes such as volcanism, magnetic field generation, and expansion/contraction, the record of which may be observable on planetary body surfaces. We suggest that Mercury exhibits characteristics of shallow sequestration of HPE and that Mars exhibits characteristics of deep sequestration. Plain Language Summary: The surfaces of Mercury, the Moon, and Mars record information about the history of volcanism, global expansion and contraction, and magnetic field generation experienced by each body. These three bodies also underwent differentiation shortly after they formed, possibly resulting in distinct layers within their mantles as well as preferential sequestration of the radioactive heat‐producing elements (HPE) primarily in one layer. We delve into the hypothesis this layering plays a pivotal role in determining when geological processes such as volcanic eruptions and global expansion and contraction can occur. We use numerical models to simulate heat transport processes in a simplified planet with the HPE sequestered in a stabilized layer either at the top or the bottom of the mantle. We find that layering in the mantle and sequestration of HPE change the way that a planet's mantle exchanges heat with the planet's core and the surface, influencing the relative timing of volcanic activity, global tectonics, and magnetic field generation, all of which can leave observable imprints on planetary surfaces. We propose that Mercury's geological history is consistent with HPE locked into a layer at the top of its mantle, whereas the geological history of Mars is consistent with a deeper distribution. Key Points: The distribution of heat‐producing elements (HPE) within a planetary mantle controls the relative timing of volcanism, tectonism, and magnetismThe geological histories of the Moon and Mars are consistent with deep sequestration of HPEThe geological history of Mercury alternatively suggests shallow sequestration of HPE [ABSTRACT FROM AUTHOR] |
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