Category Archives: Saturn’s Moons

Cassini Bids Farewell to Dione with Some Fantastic Final Views

Mosaic of Saturn's 700-mile-wide moon Dione made from nine images acquired on Aug. 17, 2015. Saturn itself covers the entire background. (NASA/JPL/SSI)

Mosaic of Saturn’s 700-mile-wide moon Dione made from nine images acquired during its “D-5” flyby on Aug. 17, 2015. Saturn itself covers the entire background. (NASA/JPL/SSI)

NASA’s venerable Cassini spacecraft may still have another two years left in its exploration of the Saturn system but on Monday, August 17, it had its final intimate visit with Dione, one of Saturn’s largest natural satellites at nearly 700 miles (1,126 km) across. On that day Cassini passed within 300 miles (480 km) of Dione at 2:33 p.m. EDT (18:33 UTC), not its closest flyby ever but certainly near enough to get some truly spectacular views of the icy moon’s ancient and cratered surface.

Check out some of Cassini’s last close-up images of Dione below:

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Hyperion in Color: a Composite from Cassini’s Last Visit

RGB color-composite of Hyperion from Cassini's May 31, 2015 flyby. NASA/JPL-Caltech/SSI. Edited by Jason Major.

RGB color-composite of Hyperion from Cassini’s May 31, 2015 flyby. NASA/JPL-Caltech/SSI. Edited by Jason Major.

Here’s a color view of Hyperion made from raw images acquired in optical wavelengths by Cassini during its flyby on May 31, 2015 – the last pass it will make by this moon during its mission. Read more about this flyby here.

Cassini To Make Its Last Pass Of Hyperion

Mosaic of Hyperion from Cassini images acquired Sept. 26, 2005. (NASA/JPL/SSI)

Mosaic of Hyperion from Cassini images acquired Sept. 26, 2005. (NASA/JPL/SSI)

This coming Sunday, May 31, the Cassini spacecraft will perform its last close pass of Hyperion, Saturn’s curiously spongelike moon. At approximately 9:36 a.m. EDT (13:36 UTC) it will zip past Hyperion at a distance of about 21,000 miles (34,000 km) – which may sound like a lot but but it’s even closer (by 17,500 miles/28,160 km) than it was when the image above was acquired.

Cassini will not come that close to Hyperion or make any flybys of it at all for the remainder of its mission, which will come to an end when it dives down into Saturn’s atmosphere in September 2017.

Read more in my article on Universe Today.

UPDATE 6/1/15: The images from the flyby are in! See a few of them below…

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Icy Tendrils in Saturn’s E Ring Traced Back to Enceladus

Cassini images of Enceladus in the E ring (top left, upper center) and computer-generated models of the same scenes. Views from 2006 and 2013, respectively. (NASA/JPL-Caltech/Space Science Institute)

Cassini images of Enceladus in the E ring (top left, upper center) and computer-generated models of the same scenes. Views from 2006 and 2013, respectively. (NASA/JPL-Caltech/Space Science Institute)

As the ice-encrusted moon Enceladus makes it way along its orbit around Saturn it gets repeatedly squeezed by the giant planet’s gravity, like a frozen stress ball with water-filled insides. This constant squeezing and relaxing generates friction heat in the moon’s crust, which could be responsible for keeping some of its internal water liquid and spraying it out into space from long canyons that cut across its southern pole. And sometimes more ice gets shot out than at other times, forming a trail of long tendrils that stretch into the “E” ring – a hazy, diffuse doughnut around Saturn made from Enceladus’ icy exhaust.

These tendrils had been observed by the Cassini spacecraft since 2006, but only now have they been positively confirmed to be the results of specific geysers on the 318-mile-wide moon.

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A Northern View of Saturn’s Stained Moon Iapetus

Saturn's moon Iapetus, imaged by Cassini on March 31, 2015 (NASA/JPL-Caltech/SSI)

Saturn’s moon Iapetus, imaged by Cassini on March 31, 2015 (NASA/JPL-Caltech/SSI)

Here’s a raw image of Saturn’s moon Iapetus, looking down on its northern hemisphere from Cassini on March 31, 2015. The moon’s signature two-toned coloration is evident as its bright icy surface is partially coated by dark material, thought to have been ejected from distant neighbor Phoebe.

Iapetus is 914 miles (1,471 km) in diameter, or about as wide as Texas and Louisiana combined. It orbits Saturn at a considerable distance of 2,212,889 miles (3,561,300 km), which is nine times farther than the Moon is from us.

Iapetus’ north pole is located just below and to the left of the centrally-peaked crater south of the brightest region in the image above. (The two prominent craters near image center are Roland and Turpin.)

Learn more about Iapetus here, and for a color version of the above image click here.

Cassini Captures Narrow-Angle, Wide-Spectrum Views of Rhea

Composite image of Saturn's moon Rhea from Feb. 9, 2015. Credit: NASA/JPL-Caltech/SSI.

Composite image of Saturn’s moon Rhea from Feb. 9, 2015. Credit: NASA/JPL-Caltech/SSI.

After spending a couple of years in an orbit riding high over the northern pole of Saturn Cassini has swung back down alongside the planet’s ringplane, in perfect alignment to once again capture views of the icy moons that reside there. The image above is a composite made from several narrow-angle camera images acquired by Cassini on Feb. 9, 2015, showing an extended color view of Rhea as the spacecraft was heading to perform a targeted flyby of the larger haze-covered moon Titan.

Saturn’s second-largest moon, the heavily-cratered Rhea wouldn’t appear this golden to our eyes; its natural colors are much more monochromatic (i.e., grey.) But Cassini can “see” in light stretching from ultraviolet to infrared, and that added range lets us see Rhea in a new light.

Read the rest of this article on Discovery News here.

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