Stratigraphy of Tectonic Features on Saturn's Satellite Dione Derived from Cassini Iss Camera Data

Introduction: Dione (1124 km in diameter) is a mid-sized icy moon of Saturn which shows a wide range in tectonic features across its surface revealing an intense geologic history. With the two highly evolved satellites Enceladus und Titan, Dione forms a set of three satellites whose surfaces have been shaped by tectonic activity on a global, not only on regional scale. Tectonic forms on Dione were first observed in Voyager camera data from the two flybys in 1980 and 1981 [1][2][3][4]. Troughs and lineaments were reported to be the most abundant type of tectonic features , scarps and ridges also occur [3][4]. During several flybys at Dione including a close flyby in Oct. 2005, the ISS NAC and WAC cameras aboard Cassini [5] have shown the tectonic features on Dione's surface in much greater detail. Especially, " wispy terrain " or " bright wispy material " observed in Voyager data which was interpreted as possibly cryovolcanic in origin [1][2][3] could be revealed as unequivocally tec-tonic by Cassini ISS [6][7]. Motivation and procedure: This work is focused on the stratigraphic sequence of tectonic events which created various sets of troughs, graben, ridges and lineaments, independent of the specific stress origins which is the topic of further work. The investigation is based on the global Cassini ISS image coverage at regional scale (150 – 500 m/pxl). For more detailed analysis, higher-resolution images from one targeted flyby at Dione and stereo imagery were used. Relative ages of these tectonic landforms are constrained by (1) crosscutting relationships, (2) by their degree of degradation , and (3) by superimposed crater frequencies. Absolute age estimates can be made with the two currently existing cratering chronology models [8][9]. Most of the tectonic features on Dione were recently named, or those with existing names as the " wispy material " (former lineae) were assigned new designa-tors (fossae or chasmata) [10]. Tectonic forms: Tectonic landforms are abundant widely across Dione and occur even in the most densely cratered plains. The following forms are observed: Troughs and graben. These features, associated with horsts in some places, are the spatially most abundant tectonic landforms on Dione. Troughs are several kilometers or a few tens of kilometers wide and up to several hundred kilometers long. Linear as well as