Gas Giant and Their Satellites: Jovian Planets – A Brief Inventory:

The largest planets in the are the ones we are least likely to visit in person.

• The distinguishing feature of Jovian (or giant) planets is their lack of a surface.

• Their composition is similar to the (mostly H and He, with small amounts of everything else). This is a remnant of how they formed.

• Their are also similar to the Sun (1 gm cm-3)

• They are also fluid bodies like the Sun, which means that they rotate differentially. • Differential rotation is like stirred in a pot. The material in the center rotates at a different speed than at the edge.

• For a we can think of its interior as a series of cylinders each moving with its own angular speed.

• The size and relative speed of the cylinders depends on the interior. • The Giant Planets also rotate very rapidly, which distorts them from a spherical sphere Oblate spheroid shape. • A cloud on the equator of is moving 45,000 miles an hour! How are we Able to Know This? Clouds!!!! • Clouds on the Jovian planets are structurally unimportant, but they can be followed to show the larger structure of the outer layers.

• In the outer solar system clouds can be made of more than just water.

• They also can be made of , , Ammonium Hydrosulfide, Phosphine, , and other Aerosol compounds.

• Each type of cloud has a different color. • Where the clouds form is a function of temperature and pressure in the ’s . • Different colors probe different levels in the atmosphere! Clouds and Mapping the Jovian Planets. The depth of the cloud and aerosol layers is determined by the temperature and pressure profiles of the atmosphere.

• Jupiter is the warmest of the Jovian planets, and it’s clouds are at the highest altitudes. This enhances their contrast.

• Watching the movement of the clouds tells us about the underlying convection patterns of the atmosphere.

• The banded structure shows zones and belts of convective motion in the atmosphere • On the clouds are deeper and the contrast lower.

and have clouds very deep and very few visible features in their atmospehres (especially Uranus). Interiors of the Gas Giants: From the combination of shape (oblateness), Rotation Rate, and composition we are able to determine the interior properties of the gas giants.

• The gas giants differ from the Sun in the way that they are organized.

• While both are composed mostly of H and He, the Sun is held up by Fusion, which heats the interior to millions of degrees, while the Jovian planets are supported by pressure.

• Each has differentiated to form a fluid mantle around a (possible) rocky core several times more massive than the , which is in turn covered by a layer of compressed gas. • In the case of Jupiter and Saturn the mantle consists of an exotic substance called ‘metallic ’.

• Uranus and Neptune have less Hydrogen, are cooler, and are smaller. Their mantle is likely to be composed of pressurized water ice. Cooling Down: The interiors of the Jovian planets are very hot (5,000-20,000 K).