Wednesday, March 04, 2009

That's no moon....

A new moon of Saturn is discovered.

Image credit: NASA/JPL/Space Science Institute

In the sequence of three images above, obtained by NASA's Cassini spacecraft over the course of about 10 minutes on October 27, 2008, you can see the path of a newly found moonlet in a bright arc of Saturn's faint G ring. The moonlet was initially seen in Cassini images from last August.

In each image, a small streak of light within the ring is visible. Unlike the streaks in the background, which are distant stars smeared by the camera's long exposure time of 46 seconds, this streak is aligned with the G ring and moves along the ring as expected for an object embedded in the ring.

Cassini scientists interpret the moving streak to be reflected light from a tiny moon half a kilometer wide that is likely a major source of material in the arc and the rest of the G ring. Debris knocked off this moon forms a relatively bright arc of material near the inner edge of the G ring, the most visible part of the ring in these images. That arc, in turn, leaks material to form the entire ring.

This view looks toward the un-illuminated side of the rings from about 5 degrees above the ringplane. The view was acquired at a distance of approximately 1.2 million kilometers from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 23 degrees.

Image scale for the first image is 7 kilometers (4 miles) per pixel. The second and third images were taken at further reduced resolution. This is definitely nowhere near the level of detail required to show surface features.

The Cassini mission has been extended until 2010, and if the spacecraft continues to function correctly, may be extended again.

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