Space Topics: Saturn
DIONE
Wispy Star Moon
Saturn's moon Dione
A distant view of Dione showcases the "wispy terrain" first observed by Voyager. A close Cassini flyby proved that the wisps were the bright walls of fractures on Dione's surface.
Credit: NASA / JPL / Space Science Institute
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Size: 1,120 kilometers - 4th largest moon
of Saturn
Orbital radius: 377,400 kilometers - 6.26 Saturn radii - within
the E ring
Orbital period: 2.737 days - about 1/6 of Titan's
Discovery: 1684 by Giovanni Domenico Cassini
Dione's globe is dominated by a star-like pattern of bright "wispy
terrain" -- or so it appeared from the Voyagers' distant views. It
was long speculated that the wispy terrain represented relatively fresh
volcanic flows of icy material. Close views from Cassini have revealed
that the wisps are not volcanic features at all. They are exposed
cliff faces, a terrain created by the fracturing and faulting of Dione's
surface. In fact, there are fractures to be seen everywhere on Dione,
representing multiple generations of tectonic events. Some slice
up craters, while others have craters superimposed on them.
Features on Dione are named for people and places from Virgil's Aeneid,
which complements similar Tethys' naming scheme (the Odyssey).
Like Tethys, Dione has little rocks keeping it company in its Lagrange points:
Helene occupies the same orbit as Dione, 60 degrees ahead, while Polydeuces
occupies the same orbit, 60 degrees behind.
Flybys of Dione
Cassini
December 15, 2005 at 01:41 UTC
“OBDI” nontargeted flyby
Closest approach altitude 72,069 kilometers (44,776 miles)
Cassini
August 1, 2005
“12DI” nontargeted flyby
Closest approach altitude 152,000 kilometers (94,000 miles)
Cassini
October 11, 2005 at 17:52 UTC
“16DI” targeted flyby [D1]
Closest approach altitude 500 kilometers (311 miles)
Map of Dione
Global map of Dione (simple cylindrical projection)
Global map centered at 180 degrees longitude (the anti-Saturnian point). The map is 2,048 pixels wide, and Dione's diameter is 1,118 kilometers, so the map resolution is 1.7 kilometers per pixel at the equator. A larger and more up-to-date version may be available at Steve Albers' website.
Credit: NASA / JPL / Space Science Institute / Steve Albers
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