论文标题
欧罗巴的半球颜色二分法是对非同步旋转的限制
Europa's Hemispheric Color Dichotomy as a Constraint on Non-synchronous Rotation
论文作者
论文摘要
欧罗巴的表面反射率表现出明显的半球二分法，由于在jovian磁层中夹着的能量颗粒对后半球的辐照增强，因此可以认为这形成。我们建议，只有在变色的时间尺度比欧罗巴相对于同步状态的旋转时间短得多，并且提供了一种使用观察到的颜色模式来限制旋转速率的方法。通过将纵向紫外线和从旅行者数据的可见颜色变化分解为正弦和余弦术语，我们没有发现非同步旋转（NSR）的可检测特征。通过两个观察性的变色模型得出了相同的结论：一个代表积极变色的表面，另一个假设表面上的当今外来源性变色为稳定状态。预期特征的幅度表示为火山口pwyll年龄的功能，用于限制变色的时间尺度。此外，我们开发了一个变色的物理模型，以验证几何模型，从而产生一致的结果。未能使用欧罗巴半球颜色二分法来识别NSR的签名，这扩大了压力起源的杰出问题，以解释欧罗巴的普遍构造特征。
Europa's surface reflectance exhibits a pronounced hemispheric dichotomy, which is hypothesized to form due to enhanced irradiation of the trailing hemisphere by energetic particles entrained in the jovian magnetosphere. We propose that this pattern can only persist if the timescale for discoloration is much shorter than that of Europa's rotation relative to the synchronous state, and provide a means for constraining the rotation rate using the observed color pattern. By decomposing the longitudinal ultraviolet and visible color variations from Voyager data into sine and cosine terms, we find no detectable signature of non-synchronous rotation (NSR). This same conclusion is reached with two observational models of discoloration: one representing an actively discoloring surface, and the other assuming that the present-day exogenic discoloration on the surface is in steady-state. Magnitudes of the expected signature are presented as functions of the age of the crater Pwyll, which is used to constrain the timescale of discoloration. Furthermore, we develop a physical model of discoloration to validate the geometric models, producing consistent results. The failure to identify a signature of NSR using Europa's hemispheric color dichotomy magnifies the outstanding problem of the origin of the stress to explain Europa's pervasive tectonic features.
