Category Archives: Cassini

Enceladus Ocean

Artist concept:  NASA/JPL-Caltech
A possible internal structure of Enceladus. Artist concept: NASA/JPL-Caltech

I love this! I know, it’s not “for sure positively” but close enough for me. I was in the “global ocean” camp, then I thought “why not” this seems perfectly reasonable.

I do have to take issue with the very last line of the ESA press release (included / linked below): “This experiment provides a crucial new piece of information towards understanding the formation of plumes on this intriguing moon,” says Nicolas Altobelli, ESA’s Cassini project scientist.  Yeah it does provide a piece, but seems like it brings up more questions than it answered. That’s awesome is what it is!

Here is the Enceladus image gallery from NASA.

The press release from ESA is excellent:

Saturn’s icy moon Enceladus has an underground sea of liquid water, according to the international Cassini spacecraft.

Understanding the interior structure of 500 km-diameter Enceladus has been a top priority of the Cassini mission since plumes of ice and water vapour were discovered jetting from ‘tiger stripe’ fractures at the moon’s south pole in 2005.

Subsequent observations of the jets showed them to be relatively warm compared with other regions of the moon and to be salty – strong arguments for there being liquid water below the surface.

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Saturn Storm

The churning atmosphere of Saturn. Copyright NASA/JPL-Caltech/SSI/Hampton University

I was having a look at the ESA Space in Images page and they had this image of the stormy atmosphere of Saturn. We tend to be more used to seeing this sort of activity in the atmospheric bands of Jupiter, Saturn shares similar storm processes (and banding) although the colors tend to be more muted. The image colors were enhanced to tease out the visual details as explained below in the ESA caption.

Like a swirl from a paintbrush being dipped in water, this image from the Cassini orbiter shows the progress of a massive storm on Saturn. The storm first developed in December 2010, and this mosaic captures how it appeared on 6 March 2011.

The head of the storm is towards the left of the image, where the most turbulent activity is shown in white, but towards the centre you can also see the trace of a spinning vortex in the wake of the storm.

This image, centred at about 0º longitude and 35º N latitude, has had its colours enhanced to help reveal the complex processes in Saturn’s weather. The white corresponds to the highest cloud tops, but to the human eye the storm would appear more as a bright area against a yellow background.
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Four Moons

Four moons of Saturn at once!  Click for larger. Credit: NASA/JPL-Caltech/Space Science Institute
Four moons of Saturn at once! Click for larger. Credit: NASA/JPL-Caltech/Space Science Institute

We get to see four of Saturn;s moons in this Cassini image. NASA describes them below. They do not comment on one of more spectacular shots of the rings Cassini has taken; they show up better in the larger versions at the NASA website.

Two pairs of moons make a rare joint appearance. The F ring’s shepherd moons, Prometheus and Pandora, appear just inside and outside of the F ring (the thin faint ring furthest from Saturn). Meanwhile, farther from Saturn the co-orbital moons Janus (near the bottom) and Epimetheus (about a third of the way down from the top) also are captured.

Prometheus (53 miles, or 86 kilometers across) and Pandora (50 miles, or 81 kilometers across) sculpt the F ring through their gravitational influences. Janus (111 miles, or 179 kilometers across) and Epimetheus (70 miles, or 113 kilometers across) are famous for their orbital dance, swapping places about every four years. They are also responsible for gravitationally shaping the outer edge of the A ring into seven scallops.
This view looks toward the sunlit side of the rings from about 47 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Oct. 11, 2013.

The view was acquired at a distance of approximately 810,000 miles (1.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 47 degrees. Image scale is 47 miles (76 kilometers) per pixel.

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Students Looking for a Project?

Continuing on this weekend’s theme:

13 years of Cassini for a Day! This is a great opportunity for both teachers and students, espeically students. Looking for a project? You could enter this and (or) use the essay at school. Surely an entry would earn some extra credit.

Students must be in grades 5 to 12 and the entry deadline is 17 April 2014. Note: that is a US deadline, other counties may have different deadlines which are not yet listed, typically they indeed different.  The International link on the site is not yet current but it will be shortly.

Check out the Cassini Scientist for a Day website.

The contest meets U.S. National English and Science Education Standards.

Cassini Scientist for a Day is an essay contest designed to give students a taste of life as a scientist.

Students study three possible targets that the Cassini spacecraft can image during a given time set aside for education. They are to choose the one image they think will yield the best science results and explain their reasons in an essay.

The three targets are:

  1. Target 1 is Saturn’s F ring. Cassini will be taking 70 images of the F ring using the spacecraft’s Narrow Angle Camera to make a movie showing how the F ring changes as it orbits Saturn.
  2. Target 2 is Saturn’s largest moon, Titan. Cassini will be taking nine images of Titan’s north polar region using its Narrow Angle Camera. These images will be stitched together to form a mosaic.
  3. Target 3 is the planet Saturn. The Cassini spacecraft will use its Wide Angle Camera and its Narrow Angle Camera to image Saturn’s north pole, studying the hurricane at the north pole and the hexagon-shaped polar vortex.


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The Saturn moon Rhea. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
The Saturn moon Rhea. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

It has been quite a while since I’ve seen the Saturn moon Rhea so I thought I’d put this recent Cassini offering up.

From Cassini:

A nearly full Rhea shines in the sunlight in this recent Cassini image.
Rhea (949 miles, or 1,527 kilometers across) is Saturn’s second largest moon.
Lit terrain seen here is on the Saturn-facing hemisphere of Rhea. North on Rhea is up and rotated 43 degrees to the left. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 10, 2013.
The view was obtained at a distance of approximately 990,000 miles (1.6 million kilometers) from Rhea. Image scale is 6 miles (9 kilometers) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

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Saturn’s D ring

Saturn’s D ring. mage Credit: NASA/JPL-Caltech/Space Science Institute

Here is the D ring of Saturn. Being faint and narrow it’s sometimes not noticed between the C ring and the planet, it just doesn’t stand out too well.

You can see part of the planet at the top of the picture the D ring next to it is the D ring. In about three years and things go as planned Cassini will pass between the two.

There are 12 stars in the image too.


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Saturn’s Aurora

On 5 April and 20 May 2013 Saturn was on the receiving end of blast of solar wind. The electrons in the solar wind and collided with hydrogen molecules and an aurora resulted.

Between the Cassini spacecraft and the Hubble Space Telescope a series of ultraviolet and infrared images were taken and put into video form.

Source Video

BTW: Snowing here, 300 to 360 mm expected overnight.

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Saturn’s F Ring

The F ring of Saturn as seen from the Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute

An interesting offering from the Cassini spacecraft. The JPL caption (below) says “the ring appears to separate from the core of the ring”. It looks more to me as if the ring isn’t so much separated as it is sort of folded, but then I’m no expert. Click the image and have a look to see what you think.

The JPL caption:

Saturn’s F ring often appears to do things other rings don’t. In this Cassini spacecraft image, a strand of ring appears to separate from the core of the ring as if pulled apart by mysterious forces.
Some ring scientists believe that this feature may be due to repeated collisions between the F ring and a single small object.
Eight stars are also visible in this image.
This view looks toward the unilluminated side of the rings from about 49 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 19, 2013.
The view was obtained at a distance of approximately 1.2 million miles (1.9 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 120 degrees. Image scale is 6.8 miles (11 kilometers) per pixel.

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The North of Saturn

A view of Saturn from Cassini. Click for larger. Image Credit: NASA/JPL-Caltech/Space Science Institute

Cassini is still alive and well around Saturn as we can see from this image of the northern hemisphere.

From JPL’s Cassini website:

Just as Saturn’s famous hexagonal shaped jet stream encircles the planet’s north pole, the rings encircle the planet, as seen from Cassini’s position high above. Around and around everything goes!

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Opposition Surge

Opposition surge at Saturn August 2013. Image Credit: NASA/JPL/Space Science Institute

The bright spot you can see on the rings of Saturn is called an “opposition surge” was taken in August 2013 and just released.

The opposition surge happens when the Sun-Ring-Cassini angle gets to zero degrees. The image here was taken through a polarized filter on the camera. The filter acts to allow only light polarized in one direction pass this reduces the scattering of light. This is very similar to the polarized lenses we have on our sunglasses.

Using the polarized filter and the size and magnitude of the spot scientists can learn about the properties of the particles making up the rings.

A nice explanation was given on an opposition surge image in the A-ring from August of 2006 – seven years before this one was taken almost to the day.

The image above was taken from a distance of 1.1 million km / 712,000 miles. The actual Sun-rings-Cassini phase angle here was seven degrees, this could account for the spot maybe not as clearly defined as the 2006 image.

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