A pair of neat developments hit the wires today — one expanding on the previous discovery of new rings around the planet Uranus (originally published back in December via Hubble Telescope observations), both involving Saturn’s rings.

First up: Blue ring discovered around Uranus

Image Credit: Imke de Pater, Heidi Hammel, Seran Gibbard, Mark Showalter, Science

The outermost ring of Uranus, discovered just last year, is bright blue, making it only the second known blue ring in the solar system, according to a report this week in the journal Science.

Perhaps not coincidentally, both blue rings are associated with small moons.

“The outer ring of Saturn is blue and has Enceladus right smack at its brightest spot, and Uranus is strikingly similar, with its blue ring right on top of Mab’s orbit,” said Imke de Pater, professor of astronomy at the University of California, Berkeley. “The blue color says that this ring is predominantly submicron-sized material, much smaller than the material in most other rings, which appear red.”

The similarity between these outer rings implies a similar explanation for the blue color, according to the authors. Many scientists now ascribe Saturn’s blue E ring to the small dust, gas and ice particles spewed into Enceladus’ orbit by newly discovered plumes on that moon’s surface. However, this is unlikely to be the case with Mab, a small, dead, rocky ball, about 15 miles across - one-twentieth the diameter of Enceladus.

Instead, the astronomers suspect both rings owe their blue color to subtle forces acting on dust in the rings that allow smaller particles to survive while larger ones are recaptured by the moon.

Very cool find! So it appears we’re seeing similar dynamics in place around two of our solar system’s ringed gas giants. I really appreciate how these findings employ prior observations performed with two of astronomers’ most powerful tools: the Keck Interferometer and the Hubble Space Telescope. Must be nice!

And now, back to Saturn: Star-Crossed Rings

Image Credit: NASA / JPL / University of Colorado

Views of Saturn’s stunning ring system from above by the Cassini-Huygens spacecraft now orbiting the planet indicate the prominent A ring contains more debris than once thought, according to a new University of Colorado at Boulder study.

This image is a false-color ultraviolet view of Saturn’s B ring (center) and A ring (right), separated by a large gap known as the Cassini Division. It shows a bright horizontal streak, created by a series of time lapse images involving a star named 26 Taurus.

The image was made over a nine-hour period as the star drifted behind the rings. The opacity of the outer A ring is most pronounced on its inner edge, indicating more ring debris is present there. The Encke Gap, much smaller than the Cassini Division, is visible near the outer edge of the A ring. The B ring is significantly more opaque than the A ring, indicating a greater density of ring material when imaged from above. The sky behind the rings glows red in the ultraviolet wavelengths from the hydrogen gas that fills the solar system.

Previous observations with the Voyager spacecraft in the early 1980s found the ring was more transparent, indicating less material, said Joshua Colwell of CU-Boulder’s Laboratory for Atmospheric and Space Physics. But new calculations based on May 2005 observations with Cassini’s Ultraviolet Imaging Spectrograph, or UVIS, indicates the opacity of the ring is up to 35 percent higher than previously reported.

Because of the uneven distribution of the ring particles - which range in size from dust grains to school buses - the transparency of the rings depends on the angle from which they are viewed, he said. The particles are arranged essentially parallel in long stringy clumps as large as 60 feet across, 16 feet thick and 160 feet long, according to models produced from observation data, said Colwell.

A nice surprise! What an ingenious method of detection.

One of the primary mission objectives for Cassini (and the scientists hard at work on the project, of course) is to make detailed determinations about the composition and characteristics of Saturn’s ring plane, as well as answer fundamental questions about the origin and fate of Saturn’s complex ring sytsem. It’s always a delight to see new tidbits of information such as this come down the pike as the mission progresses. In July, Cassini will mark it’s 2nd anniversary in Saturnian orbit, and there will be a great deal more discovered between now and the end of its planned 4-year mission duration. I can’t wait to see what we’ll learn along the way.

Oh, on a special note: stay tuned — with any luck, tomorrow we’ll be graced with new images from Mars Reconnaissance Orbiter, including the first color images from our latest venture to the red planet. The HiRISE Operations Center ( HiROC ) at the University of Arizona had planned on releasing the new MRO imagery earlier today, but unfortunately encountered server problems that spoiled the party. No worries, I’m sure they’ll be very much worth the wait — I’ll post them as soon as they become available.