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Cassini finds more rings highlighted by telltale small particles
October 12, 2006Images taken by NASA's Cassini spacecraft, looking in the direction of the Sun, have provided scientists fresh insights into the dynamic nature of the rings and, in particular, the creation of new rings made from tiny particles released from larger bodies.
Cassini findings being presented this week at the Division for Planetary Sciences Meeting of the American Astronomical Society held in Pasadena, Calif. include several new faint ring structures formed by processes acting on and within Saturn's moons and main rings.
A series of unique observations gathered in mid-September by NASA's Saturn-orbiting Cassini spacecraft as it drifted slowly through Saturn's shadow, allowed the entire ring system to be seen from a perspective that highlights microscopic ring particles: in many cases, particles only recently released into Saturn orbit. While observing from this locale, Cassini spotted, a single faint new ring, announced previously, in the shared orbit of the moons Janus and Epimetheus.
Scientists are now ecstatic to find even more rings. A second new diffuse but narrow ring is coincident with the orbit of the tiny moon Pallene, also discovered by Cassini's imaging cameras and only 4 kilometers (2.5 miles) across. Curiously, another similar-sized moon called Methone, discovered earlier in the mission in roughly the same region, does not seem to sport a ring.
A third diffuse ring-the brightest seen in the Cassini Division between the main A and B rings-was also spotted on Sept. 15 from Saturn's shadow.
Finally, a faint, very narrow, and seemingly discontinuous ringlet was also found between the broad bands of ring material in the Cassini Division. Though too small to be resolved during the September observations, it too was first seen in images taken in a geometry that enhances the visibility of small particles.
"Cassini's superior cameras and close orbits around Saturn allow us to spot fainter and narrower rings than Voyager was able to see", said Dr. Joseph Spitale, an imaging team associate working with team leader Dr. Carolyn Porco. "I wouldn't be surprised if we find more as time goes on."
All of these new rings are likely formed and maintained by impacts onto larger bodies, whether moons or large ring particles. These impacts blast material off their surfaces, creating diffuse rings in the same orbit as the parent body.
Saturn's diffuse rings are a subset that includes the E, G, and newly discovered rings. Scientists suspect that the G ring is created by impacts into bodies trapped in a remarkably bright arc in the ring. Unlike the other diffuse rings, however, Cassini observations have confirmed that the E ring is created by tiny ice particles spewing from surface jets on the geologically active moon Enceladus.
No matter how they are released, small grains are pushed about by sunlight and by electrical forces; hence their distribution tells much about the local space environment.
Imaging scientists have also noticed color variations across the diffuse rings that imply active processes sort the particles along the ring according to their sizes. Looking at the faint rings on one side of Saturn, the E ring appears to have a red core with a bluish halo, but the appearance is reversed on the right side-where there is a blue ring interior to a red ring.
According to Dr. Matt Hedman, an imaging team associate working at Cornell University in Ithaca, NY, this color variation may imply particles are being sorted by some process according to their sizes.
"These tiny grains are like spices-even a little bit of material can alter the ring's character," Hedman said.
Additionally, Cassini acquired a movie sequence and other images showing the narrowly confined G ring and its faint arc of material, which is likely held in place by a gravitational resonance with one of Saturn's moons.
Imaging Team member Joe Burns, also of Cornell University remarks, "We've been stunned by the rings' variability. Who would have thought, even a few years ago, that we'd see so many new features as the Cassini mission progressed?"
Cassini Imaging Central Laboratory for Operations (CICLOPS)
Scientists are now ecstatic to find even more rings. A second new diffuse but narrow ring is coincident with the orbit of the tiny moon Pallene, also discovered by Cassini's imaging cameras and only 4 kilometers (2.5 miles) across. Curiously, another similar-sized moon called Methone, discovered earlier in the mission in roughly the same region, does not seem to sport a ring.
A third diffuse ring-the brightest seen in the Cassini Division between the main A and B rings-was also spotted on Sept. 15 from Saturn's shadow.
Finally, a faint, very narrow, and seemingly discontinuous ringlet was also found between the broad bands of ring material in the Cassini Division. Though too small to be resolved during the September observations, it too was first seen in images taken in a geometry that enhances the visibility of small particles.
"Cassini's superior cameras and close orbits around Saturn allow us to spot fainter and narrower rings than Voyager was able to see", said Dr. Joseph Spitale, an imaging team associate working with team leader Dr. Carolyn Porco. "I wouldn't be surprised if we find more as time goes on."
All of these new rings are likely formed and maintained by impacts onto larger bodies, whether moons or large ring particles. These impacts blast material off their surfaces, creating diffuse rings in the same orbit as the parent body.
Saturn's diffuse rings are a subset that includes the E, G, and newly discovered rings. Scientists suspect that the G ring is created by impacts into bodies trapped in a remarkably bright arc in the ring. Unlike the other diffuse rings, however, Cassini observations have confirmed that the E ring is created by tiny ice particles spewing from surface jets on the geologically active moon Enceladus.
No matter how they are released, small grains are pushed about by sunlight and by electrical forces; hence their distribution tells much about the local space environment.
Imaging scientists have also noticed color variations across the diffuse rings that imply active processes sort the particles along the ring according to their sizes. Looking at the faint rings on one side of Saturn, the E ring appears to have a red core with a bluish halo, but the appearance is reversed on the right side-where there is a blue ring interior to a red ring.
According to Dr. Matt Hedman, an imaging team associate working at Cornell University in Ithaca, NY, this color variation may imply particles are being sorted by some process according to their sizes.
"These tiny grains are like spices-even a little bit of material can alter the ring's character," Hedman said.
Additionally, Cassini acquired a movie sequence and other images showing the narrowly confined G ring and its faint arc of material, which is likely held in place by a gravitational resonance with one of Saturn's moons.
Imaging Team member Joe Burns, also of Cornell University remarks, "We've been stunned by the rings' variability. Who would have thought, even a few years ago, that we'd see so many new features as the Cassini mission progressed?"
Cassini Imaging Central Laboratory for Operations (CICLOPS)
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A Long Night Falls Over Saturn's Rings
As Saturn's rings orbit the planet, a section is typically in the planet's shadow, experiencing a brief night lasting from 6 to 14 hours. However, once approximately every 15 years, night falls over the entire visible ring system for about four days.
Cassini Helps Redraw Shape of Solar System
In a paper published Oct. 15 in Science, researchers from the Johns Hopkins Applied Physics Laboratory (APL) present a new view of the region of the sun's influence, or heliosphere, and the forces that shape it. Images from one of the Magnetospheric Imaging Instrument's sensors, the Ion and Neutral Camera (MIMI/INCA), on NASA's Cassini spacecraft suggest that the heliosphere may not have the comet-like shape predicted by existing models.
NAE announces award winners John Casani and Sheila Widnall
During its 2009 annual meeting, the National Academy of Engineering (NAE) will present two awards for extraordinary impacts on the engineering profession.
CU-Boulder space scientists set for final spacecraft flyby of Mercury
NASA's MESSENGER spacecraft, which is toting an $8.7 million University of Colorado at Boulder instrument, will make its third and final flyby of Mercury on Sept. 29 -- a clever gravity-assist maneuver that will steer it into orbit around the rocky planet beginning in March 2011.
Deep Impact and Other Spacecraft Find Clear Evidence of Water on Moon
New data from the Deep Impact spacecraft and the Moon Mineralogy Mapper (M3), an instrument aboard India's recently ended Chandrayaan-1 spacecraft, provide, for the first time, clear evidence that water exists on the surface of the Moon.
Brown Scientists Announce Finding of Water on the Moon
Brown University scientists have made a major discovery: The moon has distinct signatures of water. The discovery came from a paper published in Science detailing findings from the Moon Mineralogy Mapper (M3), a NASA instrument aboard the Indian spacecraft Chandrayaan-1. Carle Pieters, professor of geological sciences at Brown, is the principal investigator of the M3 instrument and the lead author of the Science paper.
University of Hawai'i at Manoa team unravels the chemistry of Titan's hazy atmosphere
A team of University of Hawai'i at Mānoa researchers led by Ralf Kaiser, physical chemist at UH Mānoa, unraveled the chemical evolution of the orange-brownish colored atmosphere of Saturn's moon Titan, the only solar system body besides Venus and Earth with a solid surface and thick atmosphere.
Precise Radio-Telescope Measurements Advance Frontier Gravitational Physics
Scientists using a continent-wide array of radio telescopes have made an extremely precise measurement of the curvature of space caused by the Sun's gravity, and their technique promises a major contribution to a frontier area of basic physics.
Surface features on Titan form like Earth's, but with a frigid twist
"It is really surprising how closely Titan's surface resembles Earth's," says Rosaly Lopes, a planetary geologist at the Jet Propulsion Laboratory (JPL) in Pasadena, California, who is presenting the results on Friday, 7 August.
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Cassini at Saturn: Huygens Results (Springer Praxis Books / Space Exploration) by David M. Harland (Author) Cassini At Saturn – Huygens Results brings the story of the Cassini-Huygens mission and their joint exploration of the Saturnian system right up to date. Cassini entered orbit around Saturn June 2004 so this update includes 8 months of scientific data available for review, including the most spectacular images of Saturn, its rings and satellites ever obtained by a space mission. As the Cassini spacecraft approached its destination in spring 2004, the quality of the images already being returned by the spacecraft clearly demonstrated the spectacular nature of the close-range views that will be obtained. The book contains a 16-page colour section, comprising a carefully chosen selection of the most stunning images to be released during the spacecraft’s initial period of operation.... |
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Saturn: A New View by Laura Lovett (Author), Joan Horvath (Author), Jeff Cuzzi (Author), Kim Stanley Robinson (Foreword) After a journey of seven years and 2.2 billion miles, the spacecraft Cassini, with a probe named Huygens aboard, reached Saturn in July 2004, beginning a four-year tour to observe the remote planet, its rings, and its moons in depth. As a result of the spectacularly succesful Cassini-Huygens mission, photographs of astounding beauty have come streaming back to Earth, together with enough data to keep hundreds of scientists engrossed for decades. Reproduced here, in unprecedented detail and exquisite, high-quality format, are 150 of the best of those images, among them rings from the unlit side never visible from Earth and panoramas of the surface of Titan, Saturn’s largest moon. This breathtaking volume, including authoritative essays on the planetary system and the mission,... |
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