SATURN

SATURN

The 2^nd largest planet, but the least dense of all the planets. Its density is less than 1g/cm³.

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Probably has a rocky/metallic core surrounded by metallic H and a thick atmosphere of mostly H with some He, methane, and ammonia (like Jupiter).

CORE

Liquid – Metallic Hydrogen

H & He gas

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It rotates once every 10.5 hours. Its fast rotation and low density make it oblate; wider at the equator than it is between the poles.

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Saturn’s composition is similar to Jupiter’s and so it shows the same alternating bright and dark bands. Because it is much colder, Saturn’s banding is more subtle.

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Like Jupiter, Saturn great storms in its upper layers. In February of 2011 the Cassini orbiter captured this image of a storm surging through Saturn’s atmosphere.

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There is a perfectly hexagonal vortex at the north pole that is 20,000km wide. Under the right combination of temperature and pressure, this can be a natural consequence of a spinning fluid.

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Saturn’s rings were first seen by Galileo, but incorrectly identified. Christian Huygens first identified them correctly as rings around the planet.

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The rings are made of billions of chunks of mostly water-ice. Each chunk has its own orbit independent of all the rest.

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The rings are 250,000km across. They average only ~10m thick, but are up to a few km thick in places. Any chunk above or below this configuration would eventually be thrown out.

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Those chunks in the ring remain there due to a gravitational balance between Saturn, themselves, and Saturn’s many moons. Though the rings of other planets are less pronounced, the thin/flat configuration is common to all ring systems.

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Why so water-pure? 2 theories:

1. A moon of almost all water-ice broke up due to tidal forces. The chunks continue to orbit Saturn as the rings. This explains the break-up as water ice would be easily disrupted by the huge tidal forces of Saturn, but it is not so certain that a moon made almost entirely of water ice would form in the first place.

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Why so water-pure? 2 theories:

2. A rocky/icy moon formed around the proto-Saturn and had time to differentiate (denser rock sinks to the center, less dense ice floats to the top). As Saturn forms, this moon plows through the outer material and the ice is stripped away. The ice orbits as the rings, the rocky moon is one of the moons we see today.

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There are 3 main rings; A, B, C, and D. Named for the order in which they were discovered.

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Ring A is on the outside with a middle-brightness, B is in the middle and is the brightest, C is on the inside and darker than A or B. D is the darkest, inner-most ring.

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Initially A and B were thought to be the same ring.

Giovanni Cassini discovered a gap between the A and B rings known as the Cassini Division.

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The Cassini Division is ~5000km across and is actually filled with many very thin rings.

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The Cassini Division is caused by Saturn’s moon Mimas. It orbits twice for every one time a chunk within the division would orbit. Over time this orbital resonance tends to pull anything out of the division. This is exactly the same orbital phenomenon that is responsible for the Kirkwood gaps in the Main asteroid belt.

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The smaller rings within the division are caused by orbital resonances with other moons.

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There are hundreds of smaller rings (ringlets) throughout the three main rings.

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The F ring is outside of the A ring and is only 100km wide. Chunks in this ring are kept there by orbital resonance with the moons Pandora and Prometheus.

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Some moons have tilted orbits. When they pass above or below the rings they cause waves in the rings.

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Saturn’s moon Enceladus is very similar to Europa; its entire surface is a crust of water-ice.

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Saturn’s moon Enceladus is very similar to Europa; its entire surface is a crust of water-ice.

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The geyser observations and detailed studies of its orbital properties have determined that it has a moon-wide ocean of liquid water. The mechanism that keeps it in a liquid state is still undetermined.

ICE

WATER

SATURN’S MOON TITAN

Titan is Saturn’s largest moon and the 2nd largest moon in the solar system.

SATURN’S MOON TITAN

It has a thicker atmosphere than Earth made mostly of N and methane. It has a mean surface temperature of �–180°C.

SATURN’S MOON TITAN

Based on images from the Cassini orbiter and data from the Huygens lander, we have determined that Titan has rivers and lakes of liquid methane. These two together imply that the methane evaporates into the atmosphere and rains on to the surface.

SATURN’S MOON TITAN

Cryovolcanoes spew liquid water onto the surface where it quickly freezes. One theory suggests that water on Titan acts like magma and lava do on Earth. Internal heat and pressure keep the water liquid while in the interior and then it solidifies when thrust onto the surface.

SATURN’S MOON TITAN

Because Titan has �1) A thick atmosphere,�2) surface liquid, and �3) weather �some astrobiologist suggest that it may have life. If it exists, that life would be based on liquid methane rather than liquid water.