探索土卫八上黑暗物质的起源
Probing the origin of the dark material on Iapetus
摘要：
在土星的冰冷卫星中，土卫八在其前半球和后半球之间显示出惊人的二分法，前者明显比后者暗。由于卡西尼号上的VIMS成像光谱仪，现在可以在更宽的光谱范围内研究土星系统卫星的光谱特征，并且比以前可用的数据更精确。在这项工作中，我们提出了一个应用程序的G-模式方法的高分辨率，可见光和近红外数据的菲比，Iapetus和Cassini/VIMS收集，寻找成分相关性。我们还介绍了Iapetus在捕获土星系统中向内行进的尘埃颗粒的效率的动力学研究结果，以评估Poynting-Robertson阻力作为将暗物质转移到卫星的物理机制的可行性。光谱分类的结果与动力学研究的结果结合起来，描述了一个合理的物理场景的起源Iapetus的二分法。我们的工作表明，从外部土星系统的质量转移是一种有效的机制，特别是对于构成土星周围新发现的外环的粒子的大小假设范围。光谱和动力学数据都表明，土卫九是暗物质的主要来源。然而，我们提出了一个多源的情况下，现在灭绝的彗星卫星和破坏性的影响，产生了假定的碰撞家庭发挥了重要作用，在提供原始数量的暗物质。
英文摘要：
Among the icy satellites of Saturn, Iapetus shows a striking dichotomy between its leading and trailing hemispheres, the former being significantly darker than the latter. Thanks to the VIMS imaging spectrometer on-board Cassini, it is now possible to investigate the spectral features of the satellites in Saturn system within a wider spectral range and with an enhanced accuracy than with previously available data. In this work, we present an application of the G-mode method to the high resolution, visible and near infrared data of Phoebe, Iapetus and Hyperion collected by Cassini/VIMS, to search for compositional correlations. We also present the results of a dynamical study on the efficiency of Iapetus in capturing dust grains travelling inward in Saturn system to evaluate the viability of Poynting-Robertson drag as the physical mechanism transferring the dark material to the satellite. The results of spectroscopic classification are used jointly with the ones of the dynamical study to describe a plausible physical scenario for the origin of Iapetus' dichotomy. Our work shows that mass transfer from the outer Saturnian system is an efficient mechanism, particularly for the range of sizes hypothesised for the particles composing the newly discovered outer ring around Saturn. Both spectral and dynamical data indicate Phoebe as the main source of the dark material. However, we suggest a multi-source scenario where now extinct prograde satellites and the disruptive impacts that generated the putative collisional families played a significant role in supplying the original amount of dark material.
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