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The truth is that I have read a lot and I have become confused, the underground sea that Titan has, is it water or hydrocarbons, is anyone certain?

Fred
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Valentino Zaffrani
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  • Reading between the lines in the wikipedia refs seems to suggest it is water, given that ELF waves are bouncing off the interface between it and the ice layer adjacent. I think you need a conductive layer for that, which is harder to come by with a hydrocarbon ocean. I'm no astronomer or geologist though, so I could easily be wrong. – Starfish Prime Feb 28 '20 at 21:35
  • @Machavity questions about planetary science are certainly on-topic here. I've added the tag (over 200 posts!) You shouldn't just unilaterally decide something is off topic without any familiarity with the rest of the community's views. See Is planetary science on topic? in our Community Policy Repository. Also review "light touch" since you're currently aspiring to be a moderator of this community. – uhoh Feb 29 '20 at 00:33
  • @uhoh Thanks for the link. I'll definitely read up – Machavity Feb 29 '20 at 02:22
  • Wait does this count as a duplicate as Valentino asked this on Astronomy as well? https://astronomy.stackexchange.com/questions/35350/underground-sea-in-titansaturns-moon-water-or-hydrocarbons – Barry Jenakuns Feb 29 '20 at 04:26
  • Why not both? Titan could have watery and hydrocarbon liquids underground, in different layers. – Oscar Lanzi Feb 29 '20 at 10:54
  • @Hug This was asked here first 2020-02-28 20:26:28z. The comment is gone now but there was a comment saying that this is off-topic in Space SE. Nearly an hour after this question was posted, at 21:23:07 the OP also posted the question in Astronomy. Since the comment is now gone we can' see the timing or if that's what lead the OP to post in Astronomy. Now we have cross-posting and the outcome we always try hard to avoid; answer fragmentation (an answer in each SE site). – uhoh Feb 29 '20 at 13:36
  • This is why comments "hey you did something wrong!" without advice on the best way to resolve the perceived (and in this case incorrectly so) problem is not helpful. – uhoh Feb 29 '20 at 13:38
  • @uhoh Cheers for the advice. So would a better comment on my behalf look like: "As this is a crosspost of the question Valentino asked on Astronomy, I would recommend Valentino delete the question on one of the websites." ? – Barry Jenakuns Mar 01 '20 at 11:11
  • @Hug Since you pointed out the crosspost I replied to your comment but it was written for general consumption. In this case yes I usually advise a well-meaning cross-poster that they should delete one and give some advice which one might be the better choice. In this case that wouldn't have been the right advice because the other one already had an answer by then and the SE interface makes it nearly impossible to delete your question once someone has taken the time to write an answer. – uhoh Mar 01 '20 at 11:16
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    @uhoh Yeah, in this case the right thing is to leave both open since they're both on topic on the respective sites and they both have positive scoring answers. – called2voyage Mar 01 '20 at 16:37

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Underground liquid methane has been proposed as a source of the liquid in the methane-rich lakes on Titan, but it is not an ocean. Rather, as is summarized here it penetrates pores in the icy solid, similar to water in the pores of Earth's rock below the surface. The hydrocarbon liquid is not proposed to interact with the water (or water-ammonia) ocean below.

Cited reference: S. P. Falk, J. M. Lora, "Titan’s climate patterns and surface methane distribution due to the coupling of land hydrology and atmosphere", Nature Astrinomy (2019). https://www.nature.com/articles/s41550-019-0963-0

Oscar Lanzi
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There seem to be two different kinds of liquid system operating simultaneously on Titan: one of these is the system of hydrocarbon lakes you are thinking of, the other though is much larger and underneath the visible surface crust those lakes rest on which, itself, is actually water ice that is so hard due to the extremely low temperatures (94 K) that it is about as hard and firm as rock - "water rock", so to speak, or "rockwater", if you prefer. But if you go deep enough down, it gets warmer, for the same reason as it gets warmer when going down into the Earth, and that means eventually you get up to the freezing point - 273 K(*) - of water at which point there is believed to start a more conventional water ocean, like those on other moons such as Enceladus, and Jupiter's Europa. The two systems are very different and physically incompatible with each other: the rockwater layer is what provides the necessary separation.

(*) Note: due to the overburden pressure, it will be somewhat higher. Also, it is believed this water will likely be a water/ammonia mix, so you should take this as more illustrative, the actual point at which the rockwater melts to water/ammonia mix will be lower, e.g. a 25% by mass solution of ammonia in water melts at about 216 K.

The_Sympathizer
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  • Having ammonia in the water would make hydrocarbons more soluble (ammonia is less polar). Would be interesting to see how much hydrocarbon gets down to the water/ammonia ocean, but unless we can find plumes like those on Enceladus or Europa this possibility cannot be accessed from space. – Oscar Lanzi Mar 03 '20 at 16:17