Category Archives: Cassini

Tethys and Hyperion


Credit: NASA/JPL-Caltech/Space Science Institute

 Original caption released with image:

Saturn’s moons Tethys and Hyperion appear to be near neighbors in this Cassini view, even though they are actually 930,000 miles (1.5 million kilometers) apart here. Tethys is the larger body on the left.

These two icy moons of Saturn are very different worlds. To learn more about Hyperion (170 miles or 270 kilometers across), see Odd Hyperion; to learn more about Tethys (660 miles or 1,062 kilometers across) see Dark Belt of Tethys.

This view looks toward the trailing side of Tethys. North on Tethys is up and rotated 1 degree to the left. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 15, 2015.

The view was acquired at a distance of approximately 750,000 miles (1.2 million kilometers) from Tethys. Image scale is 4.4 miles (7.0 kilometers) per pixel. The distance to Hyperion was 1.7 million miles (2.7 million kilometers) with an image scale of 10 mile (16 kilometers) per pixel.

Nearing The Solstice


Saturn is nearing the northern-hemisphere solstice.  The shadow on the rings is shortening as the time gets closer in this image taken in May 2016 – compare to this image taken in 2007.

Notice the shadow is just beyond the Cassini Division, by the time the solstice gets here in May 2017 the shadow will be just past the half-way point of the B-ring (the wide light colored ring).  A year to wait for the solstice might seem like a long time, but consider it takes about 29.5 Earth-years for ONE Saturn year.  Visit our Saturn page for a lot more information on the planet and the moons.

Shadows on the Saturn system are not new.  Years before the Cassini spacecraft took these images, a gentleman named Robert Hooke noted shadows in drawings he made of Saturn in 1666.

Cassini took this image from about 3.2 million km / 2 million miles and there are a couple of things other than the shadow to take note of:  the northern polar vortex stands out nicely and the moon Mimas is visible to the lower left of the planet.

Image: NASA/JPL-Caltech/Space Science Institute

Saturn’s Atmosphere


Cassini gives us this close-up view of Saturn’s swirling atmosphere. The Juno mission to Jupiter may help us understand what is going on inside Saturn as well.  You will notice a “ring” on the right side in the dark band.  This is an artifact, quite possibly a bit of dust.

This image was obtained by Cassini (Image Credit: NASA/JPL-Caltech/Space Science Institute) on 20 July 2016.

Bending Light at Saturn


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


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


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


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


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


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.


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.
Continue reading

The Crescent of Titan


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