  The trailing hemisphere of Dione is characterized by the Wispy Terrain, where
it exhibits a hemispheric-scale network of extensional tectonic faults
superposed on the moon's cratered surface. The faults likely reflect past
endogenic activity and Dione's interior thermal history. Although fresh
exposures of pristine scarps indicate that the timing of the faulting is
relatively recent, the absolute age of the faulting remains uncertain. To
estimate the timing of the faulting, we investigated stratigraphic
relationships between impact craters and faults. Using high-resolution images
obtained by ISS cameras onboard the Cassini spacecraft, we investigated craters
with diameters exceeding or equal to 10 km that coincide spatially with the
faults, and classified the craters as crosscut craters or superposed craters.
As a result, at least 82% of the craters were interpreted as clear examples of
crosscut craters and 12% of the craters were interpreted to be candidates of
superposed craters, although stratigraphic relationships are often ambiguous.
The paucity of superposed craters and a predicted cratering rate indicate that
the faulting of the Wispy Terrain is 0.30-0.79 Ga. If 12-18% of the craters are
assumed to be superposed, the timing of the faulting could be in the range
0.30-0.79 Ga. However, it is possible that the faulting of the Wispy Terrain is
still ongoing.
