That's no moon, that's a space station!

[aaglo]

Text related to the picture:

http://www.space.com/imageoftheday/image_of_day_050111.html

Yep, it's another space station around the saturn. Mimas has the huge 'crater' (the scientist call it a crater - right ). Now Iapetus is found out to have a distinctive waist line

So, what's next? Titan is found to be habitated by ... some beings?

 

[SeleucusNicator]

It also looks unfinished, like the Return of the Jedi Death Star.

 

[Perfection]

Ya know, Iapetus is known for having a light side and a dark side.

 

[BasketCase]

Damitahell, somebody leaked the Pentagon's new military space station to the press.....

 

[Pirate]

That's awesome. There must be a forested moon with little teddy bears running around nearby. Hyugens went to the wrong place!

One wonders how a big gas giant like saturn has so many rocky moons (and rings). That planet must have a rocky core. Do we know for sure?

 

[Perfection]

One wonders how a big gas giant like saturn has so many rocky moons (and rings). That planet must have a rocky core. Do we know for sure?

Well, Saturn's moons (and infact all large moons of gas giants except Io) are considered Icy not rocky. These things have small rocky cores but are mostly covered in ice. All planets to have a metal/rock core in them, it's just that the gas giants were far enough away from the sun and big enough to develop massive gas atmospheres.

Oh and a note about Io, it used to actually be Icy, but tidal forces heated the moon up and cooked off the ice

 

[Lord Sankra]

That's awesome. There must be a forested moon with little teddy bears running around nearby. Hyugens went to the wrong place!

One wonders how a big gas giant like saturn has so many rocky moons (and rings). That planet must have a rocky core. Do we know for sure?

Jupiter and Saturn has by far the most gravitational pull in the solar system (Jupiter: 317,8 earth masses - Saturn: 95,16 earth massses), except for the sun off course. Jupiter has 2,5 the combined mass off all the other planets, satellites, asteroids, meteroids and comets in our solar system. By the planets average densities, avg den for Jupiter: 1326 kg/m^3, Saturn 687 kg/m^3, pluss the composition of their atmospheres, we can conclude that Jupiter consist approximately of 71% hydrogen, 24% helium and 5% heavier ellements.. In the case of Saturn, 92% hydrogen, 6% helium and 2% other substances. In short, both planets cotain a rocky core..

 

[Bluemofia]

Better picture of the natural "Death Star":

 

[Perfection]

Better picture of the natural "Death Star":

That's Mimas, the Above is Iapetus.

 

[Pirate]

Well, Saturn's moons (and infact all large moons of gas giants except Io) are considered Icy not rocky. These things have small rocky cores but are mostly covered in ice. All planets to have a metal/rock core in them, it's just that the gas giants were far enough away from the sun and big enough to develop massive gas atmospheres.

Thanks. By "rocky" I meant "solid". What is the definition of "rocky" according to astronomers? Is it minerals, non-water, non-metal? Are those our 3 choices for solid material? (rocky, ice, metals)

 

[Renata]

Looks like a walnut to me.

Renata

 

[Perfection]

Thanks. By "rocky" I meant "solid". What is the definition of "rocky" according to astronomers? Is it minerals, non-water, non-metal? Are those our 3 choices for solid material? (rocky, ice, metals)

It's really rocky or icy (at least in our solar system) rocky being basicly composed of a metal core with a layer above composed of a combination of metals and silcon and some other heavy stuff, icy being basicly a core like a small rocky world with a large additional layer of ice around it.

 

[Lord Sankra]

The core of Jupiter is probably several times more massive than earth. It's surrounded by a layer of liquid "ices" (water, ammonia, methane etc) On top of this is a layer of helium and liquid metallic hydrogen and an outermost layer composed primarily of ordinary hydrogen and helium. What we see of Jupiter, is near the top of this outmost layer.
Saturn internals is similar to that of Jupiter, but its core make up a larger fraction of its volume, and its liquid metallic hydrogen mantle is shallower than that of Jupiter..

On a side note, both planets emit more energy than they recive from the sun, indicating that their both cooling.

 

[Perfection]

On a side note, both planets emit more energy than they recive from the sun, indicating that their both cooling.

Both? From what I've heard, it was only Jupiter

 

[Lord Sankra]

Both? From what I've heard, it was only Jupiter

In fact, if we take Saturn's smaller mass into account, it releases about 25% more energy from its interior on a per-kg basis than Jupiter. The explanation might be that helium is raining out of Saturn's upper atmosphere. Droplets of liquid helium condenses, within the cold, hydrogen-rich outer layers of the atmosphere, into raindrops which fall to the ground. Friction between these helium droplets and the sorounding gasses generates heat.

 

[Perfection]

In fact, if we take Saturn's smaller mass into account, it releases about 25% more energy from its interior on a per-kg basis than Jupiter. The explonation might be that helium is raining out of Saturn's upper atmosphere. Droplets of liquid helium condenses, within the cold, hydrogen-rich outer layers of the atmosphere, into raindrops which fall to the ground. Friction between these helium droplets and the sorounding gasses generates heat.

How can that be? The critical temperature of Helium is 5.19K, that's far too cold for Saturn!

 

[Lord Sankra]

How can that be? The critical temperature of Helium is 5.19K, that's far too cold for Saturn!

More info: Jupiter and Saturn and also this pdf more on Saturn


Quote : "Saturn is sufficiently smaller than Jupiter that it never reached the red-hot stage in its early youth. Hence there has been ample time in the 4.5 billion years for this planet to cool down much further than its giant neighbour. Why is it emitting so much energy? At sufficiently high pressures and temperatures, liquid helium dissolves in liquid hydrogen in the same way that a cook can dissolve large amounts of sugar in hot water. But just as the cook has trouble stiring sugar into cold water, at the lower temps in Saturns interior, helium does not dissolve. Droplets of helium form in the liquid hydrogen, and being more dense they move toward the centre of the planet, like vinegar separating from the olive oil in a salad dressing. This is very slow helium rainfall and once again gravitational energy is converted into heat and ultimately radiated into space. We can test this theory by seeing if the abundance of helium relative to that of hydrogen to be much smaller in Saturn’s atmosphere compared to that of the sun. Voyager infrared spectometer measurements showed exactly this result. The amount of missing helium is consistent with a rate of helium precipitation that would produce the extra energy that Saturn and Jupiter radiate."