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Enceladus' "crispy & fractured" surface
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(...) The rims and interiors of many craters seem to be sliced by a pervasive system of narrow, parallel grooves into slabs or lanes that typically are about 1 Km in width. The widely varied appearances of fractures in this region attest to the fact that the surface of Enceladus has been shaped by a long history of intense tectonic activity. The oldest fractures are characterized by a soft, muted appearance and are overprinted by numerous, superimposed impact craters. More recent fractures exhibit topographic relief that is relatively "crisp" in appearance, and they appear to slice through pre-existing impact craters and older fractures. On the right side of the image is a conspicuous and twisted network of ridges and troughs forming a distinct tectonic region on Enceladus. The paucity of craters and the sharp appearance of the topography in this area indicate that this is a relatively young terrain on Enceladus. One possibility is that the walls of the fractures expose outcrops of solid ice, or ice with different grain-sizes compared to powdery surface materials that blanket flat-lying surfaces. It is also possible that the color identifies some compositional difference between buried ice and ice at the surface. The distinct coloration of "youthful" fracture walls are nearly absent in the oldest fractures. This is consistent with the possibility that the older fractures are covered with a drape of particulate material which mantles nearly all the oldest features on the satellite.
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(Dettagli)
