Category Archives: Cassini

Bending Light at Saturn

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Reflecting and refracting, click the image to see a larger version.

Image: NASA/JPL-Caltech/Space Science Institute

The original caption from NASA:
Saturn’s A and F rings appear bizarrely warped where they intersect the planet’s limb, whose atmosphere acts here like a very big lens.

In its upper regions, Saturn’s atmosphere absorbs some of the light reflected by the rings as it passes through. But absorption is not the only thing that happens to that light. As it passes from space to the atmosphere and back out into space towards Cassini’s cameras, its path is refracted, or bent. The result is that the ring’s image appears warped.

This view looks toward the sunlit side of the rings from about 18 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 9, 2016.

The view was acquired at a distance of approximately 1.1 million miles (1.8 million kilometers) from the rings and at a Sun-rings-spacecraft, or phase, angle of 112 degrees. Image scale is 7 miles (11 kilometers) per pixel.

Cassini’s Unique View Of Enceladus

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A unique view of the moon Enceladus thanks to the Sun-Saturn-Spacecraft geometry. Below is zoomed in on the Enceladus region.

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NASA’s caption:
Wispy fingers of bright, icy material reach tens of thousands of kilometers outward from Saturn’s moon Enceladus into the E ring, while the moon’s active south polar jets continue to fire away.

This astonishing, never-before-seen structure is made visible with the sun almost directly behind the Saturn system from Cassini’s vantage point. The sun-Enceladus-spacecraft angle here is 175 degrees, a viewing geometry in which structures made of tiny particles brighten substantially.

These features are very likely the result of particles injected into Saturn orbit by the Enceladus geysers: Those injected in the direction of the moon’s orbital motion end up on larger, slower orbits and trail Enceladus in its orbit, and those injected into the opposite direction end up smaller, faster orbits and lead Enceladus. (Orbital motion is counter-clockwise.) In addition, the configuration of wisps may hint at an interaction between Saturn’s magnetosphere and the torrent of particles issuing from Enceladus.

In addition to the wisps, another unexpected detail is the dark gore in the center of the ring, following the moon in its orbit, likely brought about by the sweeping action of Enceladus as it orbits in the center of the E ring.

The view looks down onto Enceladus (505 kilometers, or 314 miles across) from about 15 degrees above the ringplane. Tethys (1,071 kilometers, or 665 miles across) is visible to the left of Enceladus.

The image was taken in visible light with the Cassini spacecraft wide-angle camera on Sept. 15, 2006, at a distance of approximately 2.1 million kilometers (1.3 million miles) from Enceladus. Image scale is 128 kilometers (80 miles) per pixel.

Image and caption: NASA/JPL/Space Science Institute

Saturn and Enceladus

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Another beautiful image from the Cassini spacecraft orbiting around Saturn.

From NASA:
At first glance, the most obvious features in this image from NASA’s Cassini spacecraft are Saturn’s rings and the icy moon Enceladus. Upon closer inspection, Saturn’s night side is also visible (near top center), faintly illuminated by sunlight reflected off the rings.

In this view, icy Enceladus (313 miles or 504 kilometers across) hangs in the space between Cassini and the giant planet.

This view looks toward the sunlit side of the rings from 0.14 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Aug. 18, 2015.

The view was acquired at a distance of approximately 87,000 miles (139,000 kilometers) from Enceladus. Image scale is 5 miles (8 kilometers) per pixel.

Image: NASA/JPL-Caltech/Space Science Institute

Janus and Mimas

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About the image:
Saturn’s moons Janus and Mimas coast in their silent orbits beyond the rings in this view from NASA’s Cassini spacecraft. The ansa, or outer edge of the rings, is visible at left. Janus hangs above center, while Mimas shines at right. Owing to its irregular shape, Janus’ terminator — that line which separates day from night — is jagged, while Mimas’ smooth terminator belies its round shape and larger size.

The image was taken in green light with Cassini’s narrow-angle camera on Oct. 27, 2015.

The view was acquired at a distance of approximately 598,000 miles (963,000 kilometers) from Janus and at a Sun-Janus-spacecraft, or phase, angle of 86 degrees. Image scale at Janus is 3.6 miles (5.8 kilometers) per pixel. The distance to Mimas was 680,000 miles (1.1 million kilometers) for an image scale of 4.1 miles (6.6 kilometer) per pixel.

Image and caption: NASA/JPL-Caltech/Space Science Institute

Prometheus at Work

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From JPL:
Most planetary rings appear to be shaped, at least in part, by moons orbiting their planets, but nowhere is that more evident than in Saturn’s F ring. Filled with kinks, jets, strands and gores, the F ring has been sculpted by its two neighboring moons Prometheus (seen here) and Pandora. Even more amazing is the fact that the moons remain hard at work reshaping the ring even today.

Prometheus (53 miles, or 86 kilometers across) shapes the F ring through consistent, repeated gravitational nudges and occasionally enters the ring itself (clearing out material and creating a “gore” feature, see PIA12785). Although the gravitational force of Prometheus is much smaller than that of Saturn, even small nudges can tweak the ring particles’ orbits to create new patterns in the ring.

This view looks toward the sunlit side of the rings from about 12 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 21 2016.

Image and caption: NASA/JPL-Caltech/Space Science Institute

Polar Vortex on Saturn

Wow, just look at that polar vortex of Saturn in fine detail from Cassini!  For the knowledge gained on missions like this versus the cost, it is money well spent.  We should be doing more.

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Here’s the details from NASA/JPL/Space Science Institute:
Sitting at Saturn’s south pole is a vortex of monstrous proportions. The dark ‘eye’ of this feature is some 8000 km across, or about two thirds the diameter of Earth.

This image is 10 times more detailed than any previous picture of the polar vortex and shows a level of detail inside the eye that was not previously observable. Earlier images showed towering clouds around the edge of this vortex, but inside the air was thought to be mostly transparent. Here, however, a multitude of features is revealed.
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The Crescent of Titan

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Here is an image of the Saturn moon Titan.  The moon – sun – Cassini geometry was such we see Titan in a crescent phase.  Cassini’s camera took the image using the clear and blue band filters.  This is a raw image meaning it is just as it was transmitted with no processing on the ground.

The image was taken on 05 April 2016 at 11:44 UTC and received on  Earth a bit less than six hours later.

Image Credit: NASA/JPL-Caltech/Space Science Institute

Real Ring Art and More

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This Cassini image gives us a unique almost chaotic view of Saturn’s rings that look something like modern art. How does it work? The image was taken 14 degrees above the ring plane and we see the rings and their shadows on the planet.

The other thing we can see is the tiny moon Pan. Look in the narrow ring gap (known as the Encke Gap) about in the center of the image (click to enlarge it). Pan is just 28 km / 17 miles across.

Image: NASA/JPL-Caltech/Space Science Institute

and MORE:

Y-Shaped Discontinuities

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The what-discontinuities?

An excellent image by the Cassini orbiter. The “Y-shaped discontinuity” is just amazing — see below. Click the image and take a minute or two to admire the surface detail.  BTW –  I found and fixed a few image link problems.

From the Cassini team:
A sinuous feature snakes northward from Enceladus’ south pole like a giant tentacle. This feature, which stretches from the terminator near center, toward upper left, is actually tectonic in nature, created by stresses in Enceladus’ icy shell.

Geologists call features like these on Enceladus (313 miles or 504 kilometers across) “Y-shaped discontinuities.” These are thought to arise when surface material attempts to push northward, compressing or displacing existing ice along the way. Such features are also believed to be relatively young based on their lack of impact craters — a reminder of how surprisingly geologically active Enceladus is.

This view looks towards the trailing hemisphere of Enceladus. North is up. The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on Feb. 15, 2016.

The view was obtained at a distance of approximately 60,000 miles (100,000 kilometers) from Enceladus. Image scale is 1,900 feet (580 meters) per pixel.

The Cassini Division

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The Cassini site has a labeled picture here you might find helpful.

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Keep an eye out for local Yuri’s Night Celebrations, you probably have one near you (no matter where you are and it’s a good bet a scope will be on Jupiter and/or Saturn.  Both are so worth the look if you’ve never seen them for yourself, especially Saturn – it is dazzling!

From the Cassini site:

It’s difficult to get a sense of scale when viewing Saturn’s rings, but the Cassini Division (seen here between the bright B ring and dimmer A ring) is almost as wide as the planet Mercury. (See PIA11142 for a labeled panorama of features in the rings.)

The 2,980-mile-wide (4,800-kilometer-wide) division in Saturn’s rings is thought to be caused by the moon Mimas. Particles within the division orbit Saturn almost exactly twice for every time that Mimas orbits, leading to a build-up of gravitational nudges from the moon. These repeated gravitational interactions sculpt the outer edge of the B ring and keep its particles from drifting into the Cassini Division.

This view looks toward the sunlit side of the rings from about 4 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 28, 2016.

The view was acquired at a distance of approximately 740,000 miles (1.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 76 degrees. Image scale is 4 miles (7 kilometers) per pixel.