The crustal structure of Mercury's large impact basins provides valuable insights into the planet's geological history. For a warm crust, a post-impact basin structure will viscously relax with inward flow of crustal materials toward the basin center. This effect drastically diminishes the crustal thickness contrasts and associated Bouguer gravity contrasts between the basin center and its surroundings. Here, we analyze Bouguer contrasts of 36 basins (diameter $>$300 km) located in the northern hemisphere as a proxy for viscoelastic relaxation. Thermal evolution models, assuming the present 3:2 spin-orbit configuration, are used to predict crustal temperatures. Our analysis reveals that the expected correlation between zones of warm crust and low Bouguer contrast from relaxation is not observed in the available data. This suggests that crustal temperatures have changed in the past, potentially due to a change in Mercury's orbit or to a major volcanic event associated with smooth plain formation.

中文翻译：

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基于 MESSENGER 数据的大型撞击盆地对汞的弛豫状态


水星大型撞击盆地的地壳结构为了解地球的地质历史提供了宝贵的见解。对于温暖的地壳，撞击后的盆地结构将随着地壳物质向内流向盆地中心而粘性松弛。这种效应大大减少了盆地中心与其周围环境之间的地壳厚度对比和相关的布格重力对比。在这里，我们分析了位于北半球的 36 个盆地（直径 $>$300 km）的布格对比，作为粘弹性松弛的代理。假设目前的 3：2 自旋轨道配置，热演化模型用于预测地壳温度。我们的分析表明，在现有数据中未观察到暖壳区域与松弛产生的低 Bouguer 对比度之间的预期相关性。这表明地壳温度在过去发生了变化，可能是由于水星轨道的变化或与光滑平原形成相关的重大火山事件。