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Saturn's new diffuse ring, coincident with the orbits of Saturn's moons, Janus and Epimetheus. Credit: NASA/JPL/Space Science Institute |
Saturn showed off a new ring in a snapshot just taken by NASA's Cassini spacecraft.
The spacecraft, which entered the orbit of Saturn in July 2004, also revealed other dazzling features of the ringed planet, including wispy fingers of icy material stretching out tens of thousands of miles from the moon Enceladus.
Cassini's cameras took advantage of a 12-hour backlight provided by the Sun,
which was directly behind Saturn. So as Cassini lurked in the shadow of Saturn,
the planet's rings were brilliantly backlit by the passing Sun. Called a solar
occultation, this Sun-Saturn alignment typically lasts only about an hour, but
this time it was a half-day marathon.
The lengthy illumination of Saturn allowed Cassini to map the presence of microscopic particles that are not normally visible across the ring system. This level of detail gave astronomers the sharpest view yet of Saturn's inner system, including the new ring.
Another ring
Saturn's ring system is divided into seven main divisions, each designated by a letter of the alphabet. From the innermost to outermost ring, the divisions are: D, C, B, A, F, G and E.
The new ring is a tenuous feature and lies outside the brighter main rings of Saturn, but inside the G and E rings.
The ring coincides with the orbits of Saturn's moons Janus and Epimetheus. Scientists expected meteoroid impacts on the two moons could kick off moon particles and inject them into Saturn's orbit. But they were surprised to find such a distinct ring structure in that region.
Icy fingers
The 12-hour backlight session enabled astronomers to see the entire E ring in one view, a feat that previously required several images of small sections of the ring.
The snapshot showed Enceladus sweeping through the E ring, extending wispy, fingerlike projections into the ring. The scientists suspect the 'fingers' consist of tiny ice particles being ejected from Enceladus' south polar geysers and into the E ring.
"Both the new ring and the unexpected structures in the E ring should provide us with important insights into how moons can both release small particles and sculpt their local environments," said Matt Hedman, a researcher working with team member Joseph Burns, an expert in diffuse rings, at Cornell University in Ithaca, N.Y.
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