Saturn rings and shadows create a confusing portrait.

How Saturn Got Its Stripes

How Saturn Got Its Stripes

Bad Astronomy
The entire universe in blog form
Feb. 27 2016 9:30 AM

Saturnian Shadow Play

Saturn rings and shadows
Rings, shadows, moon, and planet. Note: The dark donut on the right is a shadow from a speck of dust in the camera itself, and is not a real feature of Staurn.

NASA/JPL-Caltech/Space Science Institute

I love Cassini shots of Saturn that make me do a double-take.

The image above (taken on Feb. 11) is a little confusing, isn’t it? It took me a second to figure it out, but then it clicked into place. What you’re seeing is a narrow-angle shot of Saturn’s rings (seen as the lines going from the left to right at a slight upward angle). The rings aren’t opaque, but actually translucent. In this shot we can see through them to the cloud tops of Saturn below, where the rings are casting a shadow (the fainter arcs going from left to right at a downward angle).* They’re curved because the shadows are cast onto the curved “surface” of Saturn, distorting them.


This image, taken in 2014, might help:

Saturn shadows
The rings here are seen edge-on, and look like a line bisecting the planet. The ring shadow on Saturn's cloud tops curves along with the curvature of the planet.

NASA/JPL-Caltech/Space Science Institute

Cool, eh? And all this wasn’t even the reason the newer shot was taken! If you look in the gap in the rings, just to the left of center in the image, you’ll see a tiny dot. That’s the moon Pan, the actual target of this observation! The rings and shadow play are just happy bonuses. Pan orbits Saturn in the Encke Gap, a 325-km-wide band in the rings where Pan’s gravity has ejected most of the small icy ring particles.

Saturn is weird. Its rings are weird. Its moons are weird. Everything about it is weird.

That’s one of the reasons I love it.

Tip o' the RTG to Riding With Robots.

* Update, Feb 27, 2016: Arg! My original description of the photo was confusing, ironically. If I try to explain what I did I'll probably make it worse, so instead I just changed the description to make it more clear. If you got confused, I apologize, and to make up for it go look at this.