Explanation:
What is that dark streak below Prometheus?
Although it may look like a shadow or a trail blazed by sweeping up material,
computer simulations indicate that the dark streak is better understood as an empty path pulled away by the gravity of Saturn's small moon.
The particles don't follow
Prometheus so much as glide sideways past where Prometheus used to be.
One dark streamer
is created during each pass of Prometheus through the
F-ring that it
shepherds.
The streamers were
unpredicted and first discovered in 2004 on high resolution
images taken by the robotic
Cassini spacecraft orbiting Saturn.
Close inspection of the surface of Prometheus itself in the
above image shows interesting
structure and craters.
The Cassini spacecraft arrived
at Saturn in 2004 and, as it continues to function well, is now expected to continue to send back data and images from the distant ringed world until 2017.
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