Early resonance of Tethys and Dione; Implications for Ithaca Chasma.
Early resonance of Tethys and Dione; Implications for Ithaca Chasma.
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土卫三和土卫四的早期共振；
DOI：
10.1016/j.icarus.2018.09.025
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发表时间：
2019
期刊：
影响因子：
3.2
通讯作者：
D
中科院分区：
文献类型：
--
作者：
Hussmann;H.;Rodriguez;A.;Callegari;N.;Shoji;D
我们调查了特提斯的潮汐演化，确定了几种可能的共振情景，这些情景可能与强烈的潮汐加热和该卫星历史早期伊萨卡-恰斯马的形成有关。通过对相空间的研究，我们确定了特提斯和狄奥内可以被困在2：1平均运动共振中的初始条件。从进化模型我们可以看出，在这种共振中捕获特提斯确实是可能的。这种情况意味着特提斯在其历史早期有一个小的半长轴和土星的小Q值(高耗散率)。得到了各种共振情况，包括后来从共振中演化出来的情况。作为早期2：1共振潮汐加热的结果，特提斯的潮汐加热可以显著增强。根据共振时土星的假设耗散因子，产生的全球耗散率范围在20到数百GW之间，并可能提供与特提斯上的全球裂谷系统Ithaca Chasma形成相关的热脉冲。此外，潮汐引起的轨道膨胀将导致表面应力，从而可能触发伊萨卡星云的形成。在高纬度地区，应力模式与Ithaca Chasma断层的方向一致，而在赤道地区，应力模式与断层的方向不匹配。以前的研究表明，早期次表层海洋冻结造成的膨胀可能是解释低纬度裂谷系统形成和方向所需的另一个因素。
We investigate the tidal evolution of Tethys identifying several possible resonance scenarios that could be relevant for intense tidal heating and the formation of Ithaca Chasma early in the satellite’s history. By studying the phase-space we identify initial conditions for which Tethys and Dione can be trapped in a 2:1 mean motion resonance. From evolution models we show that capture of Tethys in this resonance is indeed possible. This scenario would imply a small semi-major axis of Tethys early in its history and smallQ-values (high dissipation rates) of Saturn. Various resonance scenarios are obtained including later evolution out of resonance. As a result of the early 2:1 resonance tidal heating can be significantly enhanced in Tethys. Depending on the assumed dissipation factor of Saturn at the time of the resonance, the resulting global dissipation rate ranges between 20 and several hundred GW and could provide the heat pulse associated with the formation of Ithaca Chasma, a global rift system on Tethys. In addition, the orbital expansion due to tides will lead to surface stresses that could trigger the formation of Ithaca Chasma. The stress pattern is consistent with the orientation of faults of Ithaca Chasma at high latitudes but the orientation does not match for the equatorial regions. Expansion due to freezing of an early subsurface ocean as suggested in previous studies could be an additional factor required to explain the formation and orientation of the rift system at low latitudes.