As Cassini begins climbing into high orbits over Saturn, it’s starting to get amazing images looking down on the rings in unprecedented detail.
When the Cassini spacecraft first arrived at Saturn on June 30 and July 1, 2004, its main engine fired up on a critical burn to slow it into orbit. As a byproduct, the cameras got the closest look of the dark side of the rings it would get for the next 13 years. Amazing as those photos were, they’re looking like VHS compared to 4K now. Years ago, mission planners designed a “Grand Finale” for the spacecraft that would loft it into high polar orbits, then plunge it into Saturn in September of 2017 (this year). A byproduct of that plan is the opportunity to take never-before-possible photos of Saturn’s rings from the sunlit as well as the dark side – at close range. Get ready: get set: look!
(Source) The photos are black-and-white because the images would smear if 3-color filters were applied in sequence while the spacecraft is moving. The amount of detail visible, though, is spectacular, and of great interest to scientists. Passage of moons farther out create gravitational tugs that create waves and fine structure. The density wave at left can be seen damping out as the peaks get closer together; scientists identify Janus and Epimetheus (the co-orbital moons) as the culprits. Of special interest is the texture dubbed “straw” between the peaks, indicative of additional perturbations between the ring particles. The regularly spaced groovy “wakes” at right are believed to originate from Pan. Those damp out to the right till they bump into another density wave. Another image posted in the press release shows features caused by large moonlets embedded in the rings. The rings, of course, are not solid, but as James Clerk Maxwell determined, are composed of separately-orbiting particles.
JPL released six images in its Jan 30, 2017 press release, which you can view at the saturn.jpl.nasa.gov website. We have to share one more here. It’s of the B-ring from the closest vantage point to date, just 51,000 kilometers:
(Note: The small, bright blemishes have not been cleaned up in the photo. They are caused by “cosmic rays and charged particle radiation near the planet.”) It’s clear that the structure of the largest and thickest ring has many more secrets to reveal; “Researchers have yet to determine what generated the rich structure seen in this view, but they hope detailed images like this will help them unravel the mystery.” Expect more eye-popping images between now and September.
OK, due to popular demand, one more for an encore: here is a cleaned-up image of the outer edge of the B-ring. The dark Cassini Division is caused by a 2:1 resonance with the moon Mimas.
We hope you enjoy these historic images. Saturn’s rings are not only beautiful, they are scientifically important. Almost no ringmaster (what I call the ring experts) believes they are as old as Saturn. The same is true of the rings of Jupiter, Uranus and Neptune: they cannot be billions of years old. There are too many physical forces tugging at them, battering them, and scattering them to be even a tenth or a hundredth the assumed age of the solar system (A.S.S.). The ringmasters will have their hands full trying to explain all this fine structure and how it can endure for so long.
Let’s take a look at how much better the new images are. Here’s one from the 2004 flyover for comparison:
They were much grainier and darker then, as you can see, but still amazing. I was there with just a few others in the Space Flight Operations Facility when these first close-up images came in late at night on the day after the flyby. I remember the gasps of the scientists and their struggle to come up with on-the-spot explanations on TV.
Those were great days, being among the first to glimpse such wonders never dreamt of by Galileo, Cassini, Huygens, Maxwell and others who had observed the rings from afar when they looked “simple” (just A, B, C, and a dark division). I relished my 14 years at JPL. Though things turned out badly for me at the end because of my witness, I still enjoy being a silent member of the Cassini team from home. —DFC