Cassini flyby data of Saturn’s C ring prompts plateau puzzlement


Newswise — ITHACA, N.Y. – Spectral information about Saturn’s rings sent by NASA’s Cassini spacecraft nearly two years ago was intended to uncover definitive scientific answers. Instead, it triggered more questions about the C-ring and its plateaus.

“The plateaus are quite prominent,” said Phil Nicholson, Cornell University professor of astronomy and a member of Cassini’s Visual and Infrared Mapping Spectrometer team. “These plateaus are four times brighter and denser than the rest of the C ring, but when we examined the ring’s infrared spectrum the plateaus were almost indistinguishable from the rest of the C ring.”

Saturn’s C ring is the planet’s innermost main ring. From an Earth-based telescopic perspective, it is the faintest ring, but it seems to sport a variety of textures. The bright bands are known as plateaus because they are flat-topped – like mesas in the Southwestern states, for example 

Nicholson expected to see a spectral difference between the plateaus and the remainder of the C ring, but did not.

“That was a surprise,” he said. “In other parts of the rings – such as the A and B rings – we do see spectral variations that track ring density and brightness.”

The plateaus have long been a puzzle, and scientists have theorized they may be due to differences in particle size within the rings, as their mass per square meter is similar to that of the rest of the C ring 

“So, when we examined the ring with the spectral camera, we expected something to look different. Now, we have no hints as to what is going on,” said Nicholson, who was funded by NASA for this research. “It is driving us a bit batty.”

Data were gathered during ring-grazing orbits from December 2016 to April 2017 and during the mission’s grand finale, when Cassini flew about Saturn’s clouds. As the spacecraft ran out of fuel, the mission team deliberately plunged it into the planet’s atmosphere in September 2017.

The paper provides new details on how features such as tiny moons sculpt the rings. It also explains how the rings are a window into the astrophysical disk processes that shape our solar system, according to NASA’s Jet Propulsion Lab 

The paper, “Close-Range Remote Sensing of Saturn’s Rings During Cassini’s Ring-Grazing Orbits and Grand Finale,” is authored by 25 astronomers, including Matt Tiscareno of the nonprofit SETI Institute and a former senior researcher in the laboratory of co-author Jo Burns, Cornell professor emeritus of astronomy and engineering; and Matt Hedman, University of Idaho assistant professor and a former senior researcher with Burns and Nicholson.

For more information, see this Cornell Chronicle story.

Cornell University has dedicated television and audio studios available for media interviews supporting full HD, ISDN and web-based platforms.

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