Venus Resurfacing Constrained by Geoid and Topography

The primary explanations for the young crater age of the surface of Venus are progressive volcanic resurfacing and a period of mobile-lid tectonics. The role of initial conditions, mantle potential temperature, and core potential temperature on Venus surface mobility are explored using 3D spherical mantle convection calculations with a lithospheric yield-stress that allows the fluid to adopt either a stagnant or mobile lid. The small offset between the center of mass and center of figure (CM-CF) of Venus is reproduced in calculations that never undergo a period of mobile-lid convection. The CM-CF offset has never been used in the evaluation of geodynamic models for Venus. The mobile-lid calculations have a CM-CF offset that is four times the observed offset and, the offset increases significantly at the onset of a mobile lid/resurfacing event. Furthermore, the rapid increase in core mantle boundary heatflow that occurs as the cold lithospheric material interacts with the core mantle boundary during a mobile-lid event is sufficient to power a core dynamo, even in the absence of inner core solidification. The core mantle boundary heatflow decays over 1 Gyr after the cessation of mobile-lid tectonics. The heatflow never reaches a level that would power a thermally-driven dynamo in calculations that do not undergo mobile-lid convection. The calculations indicate that Venus young surface age is not the result of a mobile-lid resurfacing event while progressive resurfacing is consistent with the observations.

金星表面年轻火山的成因主要可归因于渐进式的火山重塑作用以及一段具有流动盖层构造活动的时期。通过采用允许流体形成静止或流动盖层的地壳屈服应力，本研究利用三维球壳地幔对流计算探讨了初始条件、地幔潜在温度以及核心潜在温度对金星表面流动性的影响。在计算中复现了金星质量中心与图形中心（CM-CF）之间的小幅偏移，这一偏移从未经历过流动盖层对流阶段。金星CM-CF偏移在流动盖层计算中达到观测偏移的四倍，且在流动盖层/重塑事件开始时显著增加。此外，在流动盖层事件期间，冷地壳材料与核心-地幔边界相互作用而导致的快速增加的核心-地幔边界热流，足以驱动核心动力学，即使在内核未固化的情况下。在流动盖层构造活动停止后，热流在10亿年内逐渐衰减。在未经历流动盖层对流的计算中，热流从未达到足以驱动热驱动动力学的水平。计算结果表明，金星年轻表面的年龄并非由流动盖层重塑事件所致，而渐进式重塑则与观测结果相符。