Subsurface oceans: The Seventeen Seas?

[h2ouniverse]

With the relatively recent capacity for thermal evolution modelling over the entire age of solar system, and the discovery of medium-sized planetary bodies beyond Neptune, the number of potential subsurface water oceans still liquid today is increasing sharply. Bodies with a large enough density and radius are considered as potential hosting such subglacial oceans either between the icy crust and the rocky core [A] or between the icy crust and a deep layer of hot high-pressure ices .
For the sake of discussion and argument, a list of candidates:
1 - Europa [A]
2 - Enceladus [A]
3 - Ganymede
4 - Callisto
5 - Titan
6 - Triton [A]
7 - Eris [A]
8 - Pluto [A]
9 - Makemake [A]
10 - Titania [A]
11 - Oberon [A]
12 - Haumea [A]
13 - Sedna [A]
14 - Ariel [A]
15 - Charon [A]
16 - Ceres [A]
17 - Dione [A]

Who agrees with the list ? Who doesn't? Where to stop it?

 

[Bootsiuv]

Who really knows? Until we go to one of these places and prove that subsurface oceans indeed exist, it's a lot of theory and little evidence. I would like to think that several of the above mentioned places may have subsurface water, even if it's in tiny amounts.

As far as the kuiper belt objects mentioned, I'm not entirely certain that those bodies were massive enough when they formed to retain much, if any, exceptional heat within their cores after 4.5 billion years. Pluto and kin are unlikely candidates in my opinion. I would think they're icy, dead bodies throughout. They simply are too far away and too low mass to retain much heat from their formation. But who knows, I'm certainly no expert on the matter. I also don't really know how these bodies are affected by other objects around them. Some gravitational friction could be occurring which could warm them up quite a bit.

Until we go there though, it's all speculation. Comparatively speaking, matter in the liquid state is, by far, the rarest form of matter in the universe, so maybe liquid water is extremely rare, only to be found in a few hundred pockets in our galaxy.

 

[kg]

Is it possible in the case of Saturn's moon Enceladus that material from deep below the surface could be sampled? How hard would it be to sample and anylize the material venting into space from this moon? Could it be done from orbit with out any messy and expensive landing, roveing, digging or drilling?

 

[moreandless]

an Eros-style landing near one of these vents would be very cool although there are
likely no direct chem labs on board to deliver such observations nor a reliable hope
of communicating the results.

 

[CalliArcale]

Is it possible in the case of Saturn's moon Enceladus that material from deep below the surface could be sampled? How hard would it be to sample and anylize the material venting into space from this moon? Could it be done from orbit with out any messy and expensive landing, roveing, digging or drilling?

Cassini has done it already! Of course, it's a bit limited by the fact that when it was built, nobody knew it would have huge plumes to fly through, so the instruments aren't the best for the job. They've been using the cosmic dust analyzer to count density of the plume, and the spectrometer to analyze its composition as light shines on/through it. If another probe is sent to Saturn, you can bet it will have at least one instrument *specifically* designed for this task, rather than for more general purposes.

 

[h2ouniverse]

Who really knows? Until we go to one of these places and prove that subsurface oceans indeed exist, it's a lot of theory and little evidence. I would like to think that several of the above mentioned places may have subsurface water, even if it's in tiny amounts..

I must disagree with "little evidence". The first five of the list have measurements by Galileo or Cassini to support the claim. The case for Europa is very "solid" (pun intended), 99%+ probability, given the morphology, the floating-then-refrozen icebergs, and magnetometer measurements. Enceladus is extremely likely too (say 90%) given the plume analysis by Cassini. Ganymede, Callisto and Titan have a very high probability (magnetometer measurements for the first two and crust rotation measurement for Titan).
For the other twelve, granted, this is inferred from thermal evolution modelling and so less supported or not supported by measured data. I have ranked them by decreasing likelihood, imnsho.
In any case we do not speak of tiny amounts. On EACH of the 4 largest bodies of the list (so excluding Enceladus), that would represent more than the Earth's oceans in volume.

For the others, in the dwarf planet size range, this is a pity that neither Dawn nor New Horizons carry a magnetometer, for this is really a powerful mean to detect any subsurface conductive layer.
About large TNOs these two articles :

http://www.sciencedirect.com/science?_o ... f6d92aed92

http://spacescience.arc.nasa.gov/agu/ab ... chetal.pdf

Excerpt of the latter:
"We conclude that objects with a densities similar to Pluto and Triton, 2.0 g/cm3, as small as 500 km in radius, could retain liquid to the present day. Our time-dependent thermal models of KBOs show that it is possible for Charon and Quaoar and many other small KBOs to retain liquid water to the present day."

Btw, the heat source has nothing to do with distance from the sun nor with accretional heat. This latter can trigger a full differentiation as discussed in today's article on Space.com for Ganymede. But even in the absence of accretional heat or thermal heating, Pluto-sized or Charon-sized bodies have enough radiogenic elements to produce a heat peak hundreds of millions of years after their formation.. Whether this heat is enough or not to melt a part of the rock/ice mixture and to keep it liquid after 4.5 billion years is then dependent on the initial ingredients (Al26 e.g., or other isotopes for the radiosource, and ammonia, methanol or salts that act as anti-freeze)
best regards.