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首页> 外文期刊>Nature >Evidence for non-synchronous rotation of Europa. Galileo Imaging Team.
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Evidence for non-synchronous rotation of Europa. Galileo Imaging Team.

机译：欧罗巴非同步轮换的证据。伽利略成像团队。

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摘要

Non-synchronous rotation of Europa was predicted on theoretical grounds, by considering the orbitally averaged torque exerted by Jupiter on the satellite's tidal bulges. If Europa's orbit were circular, or the satellite were comprised of a frictionless fluid without tidal dissipation, this torque would average to zero. However, Europa has a small forced eccentricity e approximately 0.01 , generated by its dynamical interaction with Io and Ganymede, which should cause the equilibrium spin rate of the satellite to be slightly faster than synchronous. Recent gravity data suggest that there may be a permanent asymmetry in Europa's interior mass distribution which is large enough to offset the tidal torque; hence, if non-synchronous rotation is observed, the surface is probably decoupled from the interior by a subsurface layer of liquid or ductile ice. Non-synchronous rotation was invoked to explain Europa's global system of lineaments and an equatorial region of rifting seen in Voyager images. Here we report an analysis of the orientation and distribution of these surface features, based on initial observations made by the Galileo spacecraft. We find evidence that Europa spins faster than the synchronous rate (or did so in the past), consistent with the possibility of a global subsurface ocean.
机译：通过考虑木星在卫星潮汐凸起上施加的轨道平均扭矩，从理论上预测了欧罗巴的非同步旋转。如果欧罗巴的轨道是圆形的，或者卫星由无潮汐流的无摩擦流体组成，则该转矩将平均为零。但是，由于欧罗巴与Io和木卫三的动力相互作用而产生的强迫偏心率e很小，约为0.01，这应该导致卫星的平衡自旋速度比同步速度稍快。最近的重力数据表明，欧罗巴的内部质量分布可能存在永久性的不对称性，其大小足以抵消潮汐扭矩。因此，如果观察到非同步旋转，则该表面可能通过液体或延性冰的地下层与内部分离。调用非同步旋转来解释欧罗巴的全球星系和在旅行者号影像中看到的赤道裂谷区域。在这里，我们根据伽利略号航天器所做的初步观察结果，对这些表面特征的方向和分布进行了分析。我们发现有证据表明，欧罗巴的自旋速度比同步速度快（或者过去是这样），这与全球地下海洋的可能性一致。

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