In Saturn’s shadow, part deux

The Cassini mission to Saturn has given us one astonishing view of the ringed planet and its moons after another since 2004, but this is one for the books:

saturn_rear
Saturn’s night side, as seen by Cassini on Oct. 17, 2012 at a distance of approximately 500,000 miles (800,000 kilometers) from Saturn. Get the full-resolution image here! Image credit: NASA/JPL-Caltech/Space Science Institute

Is that amazing or what? And you really have to get the full-resolution, 6672×3104-pixel image to really grok the awesomeness. This image was created on October 17, 2012 by the Cassini spacecraft while Saturn was backlit by the Sun. In other words, this is Saturn’s night side. The image was taken when Cassini was looking “up” towards Saturn’s equator from an orbital latitude of about 19 degrees. The result is a stunning image of the planet’s silhouette, surrounded by the backlit rings.

There is a lot going on here and Phil Plait has a great breakdown of all of the features of the image, so I’ll refer you there. But I should like to point out that the green glow is light reflected by the rings onto Saturn’s cloud tops. In other words, forget moonlight, this is ringlight!

Another feature that is really cool is the diffuse band of light toward the bottom of the image. This is the outermost E-ring, which is the least dense and most diffuse of the rings. This ring comes courtesy of Saturn’s moon Enceladus, which spews geysers of water vapor and ice as it orbits Saturn.

Enceladus in Saturn’s E-ring. Enceladus appears as the dark spot in the middle of the flare at center. Image credit: NASA/JPL/Space Science InstituteNASA/JPL/Space Science Institute

It’s worth mentioning that these colors aren’t real, but are a combination of infrared, red and violet spectral filters. When combined, Saturn takes on a serene, eerie hue that reveals subtle details in its atmosphere that you simply cannot get any other way.

Since the only way to obtain an image like this is when the Cassini spacecraft is directly behind Saturn, such images are very rare. The last time this sort of image was taken was back in 2006. During that encounter, images were taken using filters to create a natural-color view of the backlit planet:

In Saturn’s Shadow – the Pale Blue Dot. Image credit: NASA/JPL/Space Science Institute

And if you haven’t, you must click that image for the full view. If you look carefully, you’ll see a pale blue dot in that image on the left side just inside G-ring. That’s Earth. That’s home. That’s us.

And we made this.

Mimas is just a speck

Once in a while, an image comes along that really helps to put the sheer size of Saturn into perspective. Check this out:

Saturn and its moon Mimas (little white speck at the top center) taken by the Casini spacecraft in near-infrared on August 20, 2012. Image credit: NASA/JPL-Caltech/Space Science Institute. Get the full-size version here.

Is that beautiful or what? This is a near-infrared image of Saturn taken by the Casini Spacecraft on August 20, 2012. Casini was about 18 degrees south of Saturn’s equator. Sunlight was coming in from the northern latitudes, so the rings are backlit and cast a deep shadow “band” in Saturn’s southern hemisphere.

But take a look at the full-size version of the image. See that little speck up top? That’s Saturn’s moon Mimas, and it’s just a speck!

Mimas, taken by the Casini orbiter. Image credit: NASA/JPL-Caltech/Space Science Institute.

Now as moons go, Mimas is rather small, just 246 miles (396 kilometers) across. But it’s easy to lose sight of exactly how small that is compared to Saturn when we see images of the moon or of the planet by themselves.

And Saturn is big. Really big. Like, 74,897 miles (120,536 kilomieters) across at it’s equator big.

Obviously, 74,897 is way more than 246, but it’s hard to comprehend the vast difference in scale between these two worlds until you can see them together like this. It’s a visual reminder of the sheer diversity of worlds within our solar system.

Saturn, down under

It’s hard to believe that the Cassini mission to Saturn has been in operation for over a decade now. So much has been learned about Saturn, its rings, and its moons, but nothing of course compares to the steady stream of jaw-dropping images like this:

Saturn, seen from its southern hemisphere by the Cassini spacecraft on 1 October 2012. Image Credit: NASA/JPL/Space Science Institute

As winter starts to set in in Saturn’s southern hemisphere, the planet’s northern hemisphere and rings are tilted toward the Sun, casting an array of shadows into the cloud tops of the southern hemisphere. So this image is looking “up” towards the southern hemisphere of Saturn, when Cassini was about 1,427,863 miles (2,297,923 kilometers) away.

That’s close enough to make out a range of features. The most striking feature is the thick black shadow cast by Saturn’s innermost ring, followed by a series of thinner shadows cast by outer rings. In fact, the shadows themselves create a kind of “negative” of the rings themselves, the rings are black and the main gap between the rings – the Cassini division – shows up as white!

Now, I love full-color images of Saturn as much as the next person. But there’s something about the raw, unprocessed black-and-white images of Saturn that are just incredible. In fact, this image was made with Cassini’s “clear” filters, which is as close to a truly raw, unfiltered image of Saturn you can get. In fact, you should really check out the full-resolution version which shows off the details in all of its awesome raw-iness.

This image also illustrates how fundamentally different it would be to live on the surface of a planet like Saturn (ignoring for the moment that Saturn doesn’t have a solid surface to live upon). Seasons would be very different at different latitudes within the hemispheres. Some regions would still see the sun during the daytime, while others would be in permanent shadow for several months. Imagine looking up at the sky to see the rings backlit by the sun every day!

To really get your mind going, imagine what would be like to live on a moon where the Sun is blocked by the rings, then unblocked, then blocked again by the rings, then unblocked, then blocked again by Saturn itself, etc. That would be an absolutely crazy diurnal cycle!