Other Saturn Moons

Moons of Saturn 2007

From top left to right: Mimas, Enceladus, Tethys, Dione, Rhea, Titan in the background, Hyperion in bottom right, Iapetus, and Phoebe

 NASA/JPL/Space Science

Wikipedia 

 

Saturn has more moons than any other planet, including Jupiter. Besides Titan, it has many satellites that are strange in there own way.

 

The second largest moon of Saturn is Rhea, which is less than half the size of the Earth's Moon. It was discovered by Giovanni Cassini in 1672. Of all bodies in the Solar System in hydrostatic equilibrium, it is the smallest, i.e. gravity and fluid pressure are in balance. It is mainly ice, and much like Titan and the Moon, it is tidally locked to Saturn. It is also the largest moon without an atmosphere.

Rhea

Image Credit:

NOAA

The third largest moon of Saturn is Iapetus. It was also discovered by Giovanni Cassini in 1671 and is the largest body in the Solar System not in hydrostatic equilibrium. It is two-toned with the leading face of the moon dark with a low albedo and the back end brighter, like the color of dingy snow. It almost resembles the yin-yang symbol. It is believed that the dark face comes from Iapetus colliding with dark carbon-rich or silicate-rich materials. It is also tidally locked with Saturn.

Iapetus

Image Credit:

NASA/Voyager

Dione is the fourth largest moon of Saturn, discovered by Cassini in 1684. Like Rhea and Iapetus (and all the moons in this post), it is an icy body. Again, it is tidally locked to Saturn and shares an orbital resonance with Enceladus of 1:2. It also has two co-orbiting satellites, Heleneand Polydeuces, located at the L4 and L5 Lagrange points for Dione. Though it is mainly water ice, its density leads us to believe that it has a rocky interior.

Dione

Image Credit:

NASA/Cassini

Tethys is the fifth largest moon of Saturn, and was discovered by Cassini in 1684. It is spherical and has a density very nearly that of water. We also know that Tethys is not very active as it is heavily crated and contains a long, deep ice crack about 500 km long and 3 km deep.

Tethys with Odysseus crater

Image Credit:

NASA/Cassini

Enceladus is the sixth largest moon of Saturn, but was not discovered until 1789 by William Herschel. As an icy body, it also has a very high albedo, making it very reflective. Not only is it an icy body, it is also an active body. The interior of Enceladus is kept hot by tidal forces between itself, Saturn, and Dione. Waper vapor geysers have been discovered erupting from the surface from the Cassini spacecraft. Some of the water vapor does fall back down as snow, but most escapes due to low gravity on Enceladus. Material in the E Ring is replenished by the erupting geysers. Under the surface ice, Enceladus is believed to have a liquid ocean which may contain organic molecules (molecules with carbon).

Enceladus

Image Credit:

NASA/Cassini

Mimas is the seventh largest of Saturn's moon, and the one that many people might recognize. It was discovered by William Herschel in 1789 and much like the other moons listed here, it is a small icy body, with many craters. It has a deep 2 km crack that was probably created early in its history. Mimas is the smallest body in the Solar System that is spherical due to self-gravity. It has a 2:1 resonance with the Cassini Division, which helps keep it clear of particles. Mimas has one really distinguishing feature, and that is a large crater in the northern hemisphere.

 

Mimas with Herschel Crater in upper left

Image Credit:

Solar Views

Death Star from Star Wars. I wonder where George Lucas got his inspiration?

 

Hyperion is the eighth largest of the major moons of Saturn, and was discovered by William Lassell, William Cranch Bond, and George Phillips Bond, all in 1848. It is the largest of the irregularly shaped moons and as seen below, looks like a potato. Its shape is best determined by the diameters along its three axes, 410 km by 260 km by 220 km.

Irregularly shaped Hyperion

Image Credit:

NASA/Cassini

Star Wars and Physics

First of all, let me point out that I love Star Wars. I am old enough that the first three movies came out after I was born, so I grew up with the legacy of Luke, Leia, Han, Chewbacca, and all the rest. Everyone has already talked about how Han Solo's line about making the Kessel Run in less than 12 parsecs is inaccurate since a parsec is a distance and if the Kessel Run is less than 12 parsecs in distance, then big deal. But that is not what I want to talk about. I'm not going to talk about lightsabers or the force, since they are part of the mythos.

I want to talk about when ships are docking on the Death Star.

In almost every scene I've seen of the Millennium Falcon or the Imperial Shuttle landing in one of the cargo bays on the Death Star, I notice two things.

One, they never show a force field being deactivated, which is not that big a deal since a force field technically is invisible.

Two, when the Millenium Falcon or the Imperial Shuttle is coming in and landing, there are people in the cargo bay. This is important because if the force field is down, the cargo bay will have no atmosphere in it. Granted, the stormtroopers or whomever could have some sort of scuba gear or self-contained breathing in their armor, but when the Millennium Falcon leaves in Episode IV, Luke, Leia, Han, and Chewbacca run to the ship without any difficulty breathing. But they leave without deactivating a force field. So did the Millennium Falcon just fly through a force field? Is there something across the opening of the cargo bay that prevents the atmosphere from leaving but allows a ship to go through? That seems a little far-fetched, but again, it is science fiction.

So is there a force field across the opening of the cargo bay to hold in the atmosphere? If there isn't, how are the stormtroopers able to breathe and for that matter, our heroes when they are leaving? If there is, how is the Millennium Falcon or the Imperial Shuttle able to travel through the force field without a problem?