Explanation:
What causes the bright streaks on Dione?
Recent images of this unusual moon by the
robot Cassini spacecraft now orbiting
Saturn
are helping to crack the mystery.
Close inspection of Dione's trailing hemisphere,
pictured above, indicates that the white wisps are composed of deep
ice cliffs dropping hundreds of meters.
The cliffs may indicate that Dione has undergone some sort of
tectonic surface displacements in its past.
The bright ice-cliffs run across some of
Dione's many craters, indicating that the
process that created them occurred later than the
impacts that created those craters.
Dione
is made of mostly water ice but its relatively high density
indicates that it contains much
rock inside.
Giovanni Cassini discovered Dione in 1684.
The above image was taken at the end of July from a distance of about 263,000 kilometers.
Other high resolution images of
Dione were taken by the passing
Voyager spacecraft in 1980.
