One look at Saturn, and it’s easy to believe the largest rings are much denser than others. But, that’s not the case according to a new study of Saturn’s B ring using data from the Cassini spacecraft.

For the first time, researchers were able to ‘weigh’ the central parts of B ring. At a glance, it appears this ring is much denser than other rings. Just look at how opaque it is. Stands to reason the more opaque B ring is, the more dense it is – right? Let’s take a look at what the researchers found.

Analysis of spiral density waves helped researchers get a handle of just how dense Saturn’s B ring really is. Cassini’s visible and infrared mapping spectrometer helped make the discovery possible by looking through the rings toward a bright star. The researchers combined multiple observations and identified several spiral density waves in the rings that can’t be seen in single observations.

Matthew Hedman, the study’s lead author, was surprised by how low the overall mass of B ring is. According to Hedman, portions of B ring are up to 10 times more opaque than the nearby A ring. Despite that, it ‘weighed’ in at only three times the A ring’s mass.

What’s going on? Here’s what Hedman had to say.

“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 Hedman.

Co-author Phil Nicholson pretty much said not everything is what it appears. “Appearances can be deceiving,” said Nicholson. “A good analogy is how a foggy meadow is much more opaque than a swimming pool, even though the pool is denser and contains a lot more water.”

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As for B ring? The latest finding is surprising, but researchers still believe the ring carries the vast majority of material in Saturn’s ring system. Plus, the measurements aren’t perfect. A more precise measurement from Cassini will be able to back up Hedman and Nicholson findings. Unfortunately, we’re going to have to wait a year or so for that.

From NASA:

In 2017, Cassini will determine the mass of Saturn alone by flying just inside the rings during the final phase of its mission. The difference between the two measurements is expected to finally reveal the rings’ true mass.

Knowing the mass of Saturn’s rings can tell researchers a lot about their age and how they formed. A less massive B ring could indicate the ring is younger, maybe just a few hundred million years old versus 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 JPL.

But, researchers will have to wait until Cassini dives perilously close to Saturn to answer those questions.

Bonus B ring pictures

Saturn’s B ring stands out because of its size, but Cassini has also captured some amazing pictures of it. This one stands out.

Saturn B ring peaks

The peaks rise as much as 2 miles above the ring plane. According to NASA, “the areas are likely populated with small moons that might have migrated across the outer part of the B ring in the past and got trapped in a zone affected by the moon Mimas’ gravity. This process is commonly believed to have configured the present-day solar system.”

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Check out this time lapse showing how the gravity from Saturn’s small moons (moonlets) are affecting the edge of B ring (top of the image).

Edge of B ring

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