Do not get tricked by Saturn rings

Do not get tricked by Saturn rings

According to a recent study of the rings using data from NASA's Cassini mission, scientists found surprisingly little correlation between how dense a ring might appear to be, in terms of its opacity and reflectiveness, and the amount of material it contains.

The new results concern Saturn's B ring, the brightest and most opaque of Saturn's rings, and are consistent with previous studies that found similar results for Saturn's other main rings.

The scientists found that, while the opacity of the B ring varied by a large amount across its width, the mass -- or amount of material -- did not vary much from place to place. They weighed the nearly opaque center of the B ring for the first time -- technically, they determined its mass density in several places -- by analyzing spiral density waves. These are fine-scale ring features created by gravity tugging on ring particles from Saturn's moons, and the planet's own gravity. The structure of each wave depends directly on the amount of mass in the part of the rings where the wave is located.

At present it's far from clear how regions with the same amount of material can have such different opacities. It could be something associated with the size or density of individual particles, or it could have something to do with the structure of the rings, said Matthew Hedman, the study's lead author and a Cassini participating scientist at the University of Idaho, Moscow. Cassini co-investigator Phil Nicholson of Cornell University, Ithaca, New York, co-authored the work with Hedman.

Research on the mass of Saturn's rings has important implications for their age. A less massive ring would evolve faster than a ring containing more material, becoming darkened by dust from meteorites and other cosmic sources more quickly. Thus, the less massive the B ring is, the younger it might be -- perhaps a few hundred million years instead of a few billion.

By 'weighing' the core of the B ring for the first time, this study makes a meaningful step in our quest to piece together the age and origin of Saturn's rings, said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California. The rings are so magnificent and awe-inspiring, it's impossible for us to resist the mystery of how they came to be.

Explaining why Saturn's rings are so bright and vast is an important challenge in understanding their formation and history. For scientists, the density of material packed into each section of the rings is a critical factor in ascribing their formation to a physical process.

The new analysis is the first to directly measure the density of mass in the ring and demonstrate that there less material in the B ring.

Hedman and Nicholson used a new technique to analyze data from a series of observations by Cassini's visible and infrared mapping spectrometer as it peered through the rings toward a bright star. By combining multiple observations, they were able to identify spiral density waves in the rings that aren't obvious in individual measurements.

Despite the low mass found by Hedman and Nicholson, the B ring is still thought to contain the bulk of material in Saturn's ring system. And although this study leaves some uncertainty about the ring's mass, a more precise measurement of the total mass of Saturn's rings is on the way.

Do not get tricked by Saturn rings