Sullivan R, Greeley R, Homan K, Klemaszewski J, Belton M J, Carr M H, Chapman C R, Tufts R, Head J W, Pappalardo R, Moore J, Thomas P
Department of Geology, Arizona State University, Tempe 85287-1404, USA.
Nature. 1998 Jan 22;391(6665):371-3. doi: 10.1038/34874.
Images obtained by the Voyager spacecraft revealed dark, wedge-shaped bands on Europa that were interpreted as evidence that surface plates, 50-100 km across, moved and rotated relative to each other. This implied that they may be mechanically decoupled from the interior by a layer of warm ice or liquid water. Here we report similar features seen in higher resolution images (420 metres per pixel) obtained by the Galileo spacecraft that reveal new details of wedge-band formation. In particular, the interior of one dark band shows bilateral symmetry of parallel lineaments and pit complexes which indicates that plate separation occurred in discrete episodes from a central axis. The images also show that this style of tectonic activity involved plates < 10 km across. Although this tectonic style superficially resembles aspects of similar activity on Earth, such as sea-floor spreading and the formation of ice leads in polar seas, there are significant differences in the underlying physical mechanisms: the wedge-shaped bands on Europa most probably formed when lower material (ice or water) rose to fill the fractures that widened in response to regional surface stresses.
“旅行者号”宇宙飞船获取的图像显示，木卫二上存在黑暗的楔形带，这些楔形带被解读为直径50至100千米的表面板块相对彼此移动和旋转的证据。这意味着它们可能通过一层温暖的冰或液态水与内部在机械上解耦。在此，我们报告在“伽利略号”宇宙飞船获取的更高分辨率图像（每像素420米）中看到的类似特征，这些图像揭示了楔形带形成的新细节。特别是，一条暗带的内部显示出平行线性构造和凹坑群的双侧对称性，这表明板块分离是从中心轴以离散的阶段发生的。图像还显示，这种构造活动的样式涉及直径小于10千米的板块。尽管这种构造样式在表面上类似于地球上类似活动的某些方面，如海底扩张和极地海域冰脊的形成，但在潜在的物理机制上存在显著差异：木卫二上的楔形带很可能是在下层物质（冰或水）上升以填充因区域表面应力而扩大的裂缝时形成的。
