The Structure of Saturn's Rings
The Structure of Saturn's Rings
复制标题
DOI：
10.1007/978-1-4020-9217-6_13
复制
发表时间：
2009-01-01
期刊：
影响因子：
--
通讯作者：
Marouf, E. A.
中科院分区：
文献类型：
--
作者：
Colwell, J. E.;Nicholson, P. D.;Marouf, E. A.
自从1610年伽利略发现土星环以来，我们对土星环结构的理解一直在稳步发展。在过去的四个世纪里，随着对环的观测的每一次进步，新的结构都被揭示出来，从惠更斯在1656年认识到环是一个圆盘，到发现主环的广泛组织及其组成间隙和小环，再到卡西尼号的观测，间接揭示了几十米大小的单个粒子团。结构的多样性与规模的范围一样广泛。主环在10（4）公里的空间尺度上具有明显的特征，这表明了截然不同的演化，甚至可能是不同的起源。在较小的尺度上，A环和C环以及卡西尼分区被几十到几百公里宽的间隙所打断，而B环则在类似尺度上充满了无法解释的光学深度变化。卫星与环中的许多结构密切相关。A环和B环的外边缘分别由Janus-Epimetheus坐标轨道和Mimas的共振引导和雕刻。在与邻近和嵌入卫星的轨道共振位置的密度波构成了A环中大部分的大尺度特征。在A环的Encke和Keeler间隙内运行的卫星会产生这些间隙，并在附近的环中产生尾迹。其他的间隙和波浪状特征有待解释。最大的环粒子，虽然质量不足以清除间隙，但会产生数百米长的局部螺旋桨状扰动。穿过A环和B环的粒子聚集成几十米宽的股线或自引力尾流，它们在引力吸积和开普勒切变之间处于平衡状态。在强密度波的峰值中，粒子在宇宙交通堵塞中堆积在一起，导致更长的链，可能是更大版本的自重力尾流。F环是土星洛希区边缘吸积和分裂的展示。团和线形成并在它们彼此相遇时被破坏，并因与附近的普罗米修斯近距离相遇而受到干扰。环中结构的动物园揭示了一个动态的系统，它在从几天到几千万年或数亿年的时间尺度上不断演变。因此，环的结构提供了对环的起源以及长期和短期演变的见解。
Our understanding of the structure of Saturn's rings has evolved steadily since their discovery by Galileo Galilei in 1610. With each advance in observations of the rings over the last four centuries, new structure has been revealed, starting with the recognition that the rings are a disk by Huygens in 1656 through discoveries of the broad organization of the main rings and their constituent gaps and ringlets to Cassini observations that indirectly reveal individual clumps of particles tens of meters in size. The variety of structure is as broad as the range in scales. The main rings have distinct characteristics on a spatial scale of 10(4) km that suggest dramatically different evolution and perhaps even different origins. On smaller scales, the A and C ring and Cassini Division are punctuated by gaps from tens to hundreds of kilometer across, while the B ring is littered with unexplained variations in optical depth on similar scales. Moons are intimately involved with much of the structure in the rings. The outer edges of the A and B rings are shepherded and sculpted by resonances with the Janus-Epimetheus coorbitals and Mimas, respectively. Density waves at the locations of orbital resonances with nearby and embedded moons make up the majority of large-scale features in the A ring. Moons orbiting within the Encke and Keeler gaps in the A ring create those gaps and produce wakes in the nearby ring. Other gaps and wave-like features await explanation. The largest ring particles, while not massive enough to clear a gap, produce localized propeller-shaped disturbances hundreds of meters long. Particles throughout the A and B rings cluster into strands or self-gravity wakes tens of meters across that are in equilibrium between gravitational accretion and Keplerian shear. In the peaks of strong density waves particles pile together in a cosmic traffic jam that results in kilometer-long strands that may be larger versions of self-gravity wakes. The F ring is a showcase of accretion and disruption at the edges of Saturn's Roche zone. Clumps and strands form and are disrupted as they encounter each other and are perturbed by close encounters with nearby Prometheus. The menagerie of structures in the rings reveals a system that is dynamic and evolving on timescales ranging from days to tens or hundreds of millions of years. The architecture of the rings thus provides insight to the origin as well as the long and short-term evolution of the rings.