PDA

View Full Version : Imagining the anti-Titan



parallaxicality
2007-Oct-13, 08:29 PM
I actually asked this question a while ago, but no one answered; not really surprising, since my post consisted of a quasi-poetic waffle that made no objective sense whatsoever (note to self: next time you seek scientific information, do not refer to the death of Socrates!). Still, if I can rein in my metamorphricising impulses, I hope I can try to get this idea out of my head in a reasonably comprehensible fashion.

OK.

On Earth, we have a crust made largely of silicates. Liquid water lies on top of the crust, and evaporates into the air, falling as rain. Underneath the crust, liquid silicates churn and bubble, bursting through the surface as volcanoes.

On Titan, the crust is made of frozen water. Liquid methane lies on top of the crust, and evaporates into the air, falling as rain. Underneath the crust, liquid water churns and bubbles, erupting in volcanoes.

We think.

So basically, what is water on Earth is crust and lava on Titan. What is water on Titan is a smelly gas on Earth.

So could we imagine a similar analogue, but in the opposite direction? A world where liquid silicates lie over a dense, solid crust, rising into the air and falling as rain.

What would the crust of such a world be? What would spew out of its volcanoes?

Nerthus
2007-Oct-13, 08:46 PM
So could we imagine a similar analogue, but in the opposite direction? A world where liquid silicates lie over a dense, solid crust, rising into the air and falling as rain.

What would the crust of such a world be? What would spew out of its volcanoes?

An iron/nickel crust would make sense, seeing how thats the next level downward here on earth if you don't count the mantle, which is mostly silicates. However I don't know what the core of such a planet would be. Maybe lead or gold?

Kaptain K
2007-Oct-13, 09:16 PM
What is water on Titan is a smelly gas on Earth.

<Minor nitpick>

Methane is actually odorless. The odor is added at the refinery to assist in leak detection.

<end nitpick>

Noclevername
2007-Oct-13, 11:01 PM
To make silicate seas and rain would require a lot of energy. If the surface of a planet had that much heat, it would also need a pretty high gravity to keep the vaporized material from flying out into space. If the heat came from the sun, the planet would probably be close enough to be fully tide-locked. If the heat was from radioactive decay- Hmm, I don't know how much of the material's content would need to be radioactive isotopes, but probably a lot. Someone who knows more than me about these topics might work out the math- how much energy would you need to make an ocean of molten silicates?

Nerthus
2007-Oct-14, 05:58 AM
To make silicate seas and rain would require a lot of energy. If the surface of a planet had that much heat, it would also need a pretty high gravity to keep the vaporized material from flying out into space. If the heat came from the sun, the planet would probably be close enough to be fully tide-locked.

The exoplanet HD 189733 b was found to have clouds of silicates in it's atmosphere with an atmospheric temperature above 1000C, and orbiting at about 3 million miles away from it's yellow dwarf star. I haven't seen anything about it being tidally locked.

It's a little odd I just happened to find this example too, I wasn't searching for it, but there it is. A little of the Badder-Meinhof effect I guess.

tusenfem
2007-Oct-14, 09:47 AM
To make silicate seas and rain would require a lot of energy. If the surface of a planet had that much heat, it would also need a pretty high gravity to keep the vaporized material from flying out into space. If the heat came from the sun, the planet would probably be close enough to be fully tide-locked. If the heat was from radioactive decay- Hmm, I don't know how much of the material's content would need to be radioactive isotopes, but probably a lot. Someone who knows more than me about these topics might work out the math- how much energy would you need to make an ocean of molten silicates?

I guess the closest you would get in our solar system would be Io.

Romanus
2007-Oct-15, 03:06 AM
I dunno...the boiling point of silica is about 2500K. It wouldn't have to be that hot to be volatile, of course, but even the melting point (~1900K) puts it above the melting point of iron, tin, copper, aluminum--of, in fact, every abundant metal. Of course, those wouldn't be in their native states...

I'm guessing the only minerals that could survive this would be the most highly refractory ones, like magnesium, calcium, and aluminum oxides. But as already mentioned, there's the question of what the planet's interior would be like, with even more extreme conditions. On Earth, water vapor is a major component of volcanic emissions; perhaps this planet would have gaseous silica and metal oxide emissions, with lavas of same. Imagine how bright it would be to the eye, with everything basically white-hot...

AK
2007-Oct-15, 05:46 AM
I dunno...the boiling point of silica is about 2500K. It wouldn't have to be that hot to be volatile, of course, but even the melting point (~1900K) puts it above the melting point of iron, tin, copper, aluminum--of, in fact, every abundant metal. Of course, those wouldn't be in their native states...

I'm guessing the only minerals that could survive this would be the most highly refractory ones, like magnesium, calcium, and aluminum oxides. But as already mentioned, there's the question of what the planet's interior would be like, with even more extreme conditions. On Earth, water vapor is a major component of volcanic emissions; perhaps this planet would have gaseous silica and metal oxide emissions, with lavas of same. Imagine how bright it would be to the eye, with everything basically white-hot...

I'd imagine senses would evolve differently on such a world (assuming it were it capable of supporting life at all). ;)

Noclevername
2007-Oct-15, 03:08 PM
The exoplanet HD 189733 b was found to have clouds of silicates in it's atmosphere with an atmospheric temperature above 1000C, and orbiting at about 3 million miles away from it's yellow dwarf star. I haven't seen anything about it being tidally locked.

It's a little odd I just happened to find this example too, I wasn't searching for it, but there it is. A little of the Badder-Meinhof effect I guess.
Thanks for the find!
(Post-Google) According to Spitzer's thermal map, it is tidally locked: http://www.spitzer.caltech.edu/Media/releases/ssc2007-09/ssc2007-09a.shtml