We catalog the global inventory of Europa's cycloids, arcuate fractures whose paths have been linked to diurnal tidal stress, and use the locations and orientations of their cusps to further test the formation mechanism of cycloids and constrain Europa's rotation state. We find that the global distribution of cycloids is better explained by a precessing spin pole than longitude translation due to nonsynchronous rotation, which is consistent with studies of Europa's strike‐slip faults and linear fractures. We also find that a small obliquity can reproduce the orientations of most cycloid cusps at their current locations, outperforming a model using stress from eccentricity alone. Matching cycloid locations and cusp orientations under these conditions implies a variable failure threshold and that most cusps form at stresses that are 50%–90% of the local peak tidal stress, suggesting that periodic deformation is causing failure through fatigue. The fact that cycloids are not observed in some regions, despite the low failure stresses implied by some cusp orientations, suggests an additional control on cusp formation that was not included in our simplified model. We hypothesize that the larger amplitude of tidal stress in some regions leads to fatigue‐induced failure after fewer tidal cycles, leading to a build‐up of cycloids in those regions. Why more linear fractures do not seem limited in location or density is still unknown. More physically informed constraints on how ice fails under low, periodic deformation and across generations of fractures would be helpful in interpreting Europa's cycloids.

中文翻译：

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倾角，岁差和断裂力学：欧罗巴全球摆线针轮种群的意义

我们对欧罗巴摆线针，弧形骨折的路径与昼夜潮汐应力有关的全球清单进行了分类，并使用其尖端的位置和方向进一步测试了摆线针的形成机理并限制了欧罗巴的旋转状态。我们发现，摆线的整体分布可以更好地解释为旋进极点，而不是由于非同步旋转而引起的经度平移​​，这与对Europa的走滑断层和线性裂缝的研究是一致的。我们还发现，小的倾角可以重现大多数摆线针尖在其当前位置的方向，仅靠偏心距的应力就能胜过模型。在这些条件下，匹配的摆线针位置和尖端位置暗示了可变的失效阈值，并且大多数尖端形成的应力为局部峰值潮汐应力的50％–90％，这表明周期性变形会由于疲劳而导致失效。尽管某些尖点方向暗示了较低的破坏应力，但在某些区域仍未观察到摆线的事实表明，在简化模型中未包括对尖点形成的其他控制。我们假设某些地区的潮汐应力幅值较大，导致潮汐循环次数减少后，会导致疲劳导致的破坏，从而导致这些地区的摆线堆积。为什么更多的线性裂缝似乎在位置或密度上似乎没有局限性仍是未知的。关于冰在低温下如何破裂的更多物理上的约束，