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Most detailed color images of Saturn’s rings, ever

View larger. | Saturn’s rings – acquired by Cassini spacecraft on July 6, 2017 – from a distance of 47,000 miles (76,000 km). Image scale about 2 miles (3 km) per pixel. Phase angle, or sun-ring-spacecraft angle, is 90 degrees. Via NASA PhotoJournal.

NASA said on September 7, 2017 that the images on this page are the highest-resolution (most detailed) color images of any part of Saturn’s rings, to date. The wonderful Cassini spacecraft, whose long-running mission at Saturn will end this week, acquired them, of course. What you’re seeing here is the sunlit side of Saturn’s rings, a portion of the inner-central part of the planet’s B Ring. NASA said:

The first image (Figure A, above) is a natural color composite, created using images taken with red, green and blue spectral filters. The pale tan color is generally not perceptible with the naked eye in telescope views, especially given that Saturn has a similar hue.

The material responsible for bestowing this color on the rings—which are mostly water ice and would otherwise appear white—is a matter of intense debate among ring scientists that will hopefully be settled by new in-situ observations before the end of Cassini’s mission.

The different ringlets seen here are part of what is called the ‘irregular structure’ of the B ring. Cassini radio occultations of the rings have shown that these features have extremely sharp boundaries on even smaller scales (radially, or along the direction outward from Saturn) than the camera can resolve here. Closer to Saturn, the irregular structures become fuzzier and more rounded, less opaque, and their color contrast diminishes.

The narrow ringlets in the middle of this scene are each about 25 miles (40 km) wide, and the broader bands at right are about 200 to 300 miles (300 to 500 km) across. It remains unclear exactly what causes the variable brightness of these ringlets and bands—the basic brightness of the ring particles themselves, shadowing on their surfaces, their absolute abundance, and how densely the particles are packed, may all play a role.

View larger. | This is a color-enhanced version of the image above, via NASA PhotoJournal.

Now look at the image above. It’s a good illustration of how space scientists try to tease information out of these images. The image is color-enhanced. NASA said:

Blue colors represent areas where the spectrum at visible wavelengths is less reddish (meaning the spectrum is flatter toward red wavelengths), while red colors represent areas that are spectrally redder (meaning the spectrum has a steeper spectrum toward red wavelengths). Observations from the Voyager mission and Cassini’s visual and infrared mapping spectrometer previously showed these color variations at lower resolution, but it was not known that such well-defined color contrasts would be this sharply defined down to the scale (radial scale) of a couple of miles or kilometers, as seen here.

Analysis of additional images from this observation, taken using infrared spectral filters sensitive to absorption of light by water ice, indicates that the areas that appear more visibly reddish in the color-enhanced version are also richer in water ice.

NASA has more to say; click here to read it.

Bottom line: Photos on this page are the highest-resolution (most detailed) color images of Saturn’s rings, ever, acquired by the Cassini spacecraft on July 6, 2017. We will miss Cassini, when its mission ends this week!

September 11, 2017

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