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So I writing a story where we terraform Titan using super heavy green house gases where the lower part of the atmosphere near the surface stays warmer. Because of this, a portion of the moon's icy crust melts leaving the planet with an ocean sitting on top of an icy crust, with another ocean below that icy crust. What my question is, would the ocean remain on top or would it "leak" through the ice and just cause the ice to rise up to the surface.

Thanks

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    $\begingroup$ Ummmm, if there are any cracks in the ice, you're going to get seepage, so the ice will rise to the top, and then melt, and then rise to the top, and then melt, and if you continue this enough, you have a huge ocean. $\endgroup$ – Gryphon Apr 14 '17 at 21:33
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    $\begingroup$ If the ocean is more than a mile or so deep, the ice may be crushed under it simply because of the pressure. The slightest weakness in the ice would cause water to rush from the upper ocean to neutralize the pressure inbalance between the top of the lower ocean (less pressure) and the bottom of the upper ocean (a lot more pressure) $\endgroup$ – arthurz12345 Apr 14 '17 at 22:31
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    $\begingroup$ Different compositions of water might do it. There are deep ocean areas right now where there are two distinct stable layers of water, the lower being extremely salty or something I forget the actual reason, but the pictures were impressive.. $\endgroup$ – Kilisi Apr 14 '17 at 23:38
  • $\begingroup$ Don’t be too quick to accept! It's best to wait at least 24 hours here on WB. $\endgroup$ – JDługosz Apr 15 '17 at 3:03
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If the composition of the lower ocean was different enough, then it could work. We have underwater lakes and rivers on Earth in deep ocean. The water in these is heavier and doesn't mix with the normal sea water.

Picture of undersea river below and undersea lake shoreline, the undersea lake in the abyssal plain even has its own waves and supports a lot of life.

Underwater river Shoreline, Huge underwater lake in Abyssal Plain

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Ice floats. I can’t imagine that the ice layer would have no cracks and faults anywhere! Look at ice dams for how water infultrates and catalizes the total failure. This will happen vertically just as well. So even if there are no natural faults and loose chunks are dealt with, the ice will crumble from being in contact with water, over time.

So yes, the water will leak through (initially) solid ice.

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Ever wondered why these ice moons are so smooth without craters? Every time a crater hits them, water cracks up and fills the whole and solidifies. Hence there would be plenty of cracks. These cracks would slowly increase in number as over years the heat from the surface makes its way towards the icy layer. In addition, as moons circle their planets, they get stretched and squashed by the gravitational pull which would further induce cracks.

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Titan is a mixed ice and rock moon. Titan is extremely cold and no liquid $H_2O$ current exists anywhere in or on the planet. You'd need to raise the surface temperature 180 C to even begin the process!

If you began warming the surface of Titan enough to melt the surface ice, then the planet would start with melt pools forming on the icy surface.

Arctic Melt Pools Arctic Melt Pools

By NASA Goddard Space Flight Center from Greenbelt, MD, USA - Ponds on the OceanUploaded by PDTillman, Public Domain, Link

Ice as shown above and we encounter in everyday life here on Earth is just one possible form that solid $H_2O$ can take. As the environment changes from that found on the surface of the Earth to higher pressures and colder temperatures, water ice can take many different other forms.

Interior of Titan
Interior of Titan
From Window2Universe

The deeper you look into Titan the more exotic the ice gets. Ice I (the ice we are familiar with) is lighter than liquid water and therefore floats. Many of these other ices are denser than liquid water and so would remain in the core.

It would take a very long time (centuries, millennia, eons?) for Titan to warm enough to have to worry about anything other melt pools gradually increasing in size - even after they'd grown to the size of substantial oceans.

When the change did occur it would be sudden and it would probably kill everyone on the surface.

Use this thought experiment. Freeze a large container of water until it's frozen solid. Put heat lamps on it shining down. You'd see a similar process to what I described above, melt pools gradually growing in size. Even after the surface had entirely melted ice would remain at the bottom with water on the top - initially. With enough heat, the ice would experience a phase change, become lighter than the water, and then the whole planet would reorganize with the ice floating to the top and the water trying to sink to the bottom which releases additional heat.

It would completely disrupt the surface of the moon. Huge tsunami, huge chunks of ice blasting up from the depths. After the moon settled again, it would probably be perfectly safe to inhabit. But how long would it take for the Moon to settle down (decades, centuries, millennia)? A thousand years is an eyeblink on geological time scales.

Something like this in reverse on a scale 100 or 1000 times larger: https://www.youtube.com/watch?v=hC3VTgIPoGU

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  • $\begingroup$ Please try H₂O rather than MathJax. You need to use \mathrm or somesuch to make the letters not be variables, and full math formatting is simply not needed here. As you have it, it's formatted wrong. $\endgroup$ – JDługosz Apr 15 '17 at 2:58
  • $\begingroup$ Ha! I read “H₂Ocan” as “H₂Ocean”, as if it were a pun. $\endgroup$ – JDługosz Apr 15 '17 at 3:00
  • $\begingroup$ Maybe I'm missing something, but everything I've read says Titan has a "rockyish" core, then a layer of high pressure ice, then a massive liquid water ocean, then an icy shell, and then the atmosphere. Here's a link science.nasa.gov/science-news/science-at-nasa/2012/… $\endgroup$ – rclev Apr 15 '17 at 3:50
  • $\begingroup$ The link I provided shows the core as mostly rock with some high density ice mixed in. It does not show any liquid subsurface ocean. However, I'm perfectly willing to believe it does have a liquid ocean. $\endgroup$ – Jim2B Apr 15 '17 at 6:31
  • $\begingroup$ But it doesn't change the overall scenario. Eventually as you heat the surface, the planet will reorganize with ice I at the top and the liquid water below that. When that happens, it'll annihilate or sink everything on the surface. $\endgroup$ – Jim2B Dec 25 '17 at 17:30

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