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Section 1: Non-Duplicate Proofs.

Section 2: Background, THE QUESTION, and Useful Info.

Section 3: Other cited ways of preventing.

Section 4: Sources and Additional Resources.

Section 5: TL;DR


Non-Duplicate Proofs This is not a duplicate of Tidal lock on a water moon. The answer provided there does not answer this question (or that one fully either). I am providing these specific proofs because of the last comment made by @Ash on another post of mine (Can you have an eccentric horseshoe orbit for long?) insisting that the resources in an answer to a question determines its duplication, and not the question itself. If these are not satisfactory, I am also providing question based proofs of non-duplication.

Answer based proofs

The answer provided by bowlturner makes many generalizations, which don't always stand true.

  1. bowlturner insists that those worlds that are close enough to the sun to have liquid water would constantly be losing it, which in and of itself may be true, but given a high enough escape velocity as well as a thick enough atmosphere and magnetosphere, the loss would prove negligible on time scales of millions to billions of years, not to mention possible reintroduction of water from other sources. He does not mention escape velocity, and also provides an answer based on little to no atmosphere as well as magnetosphere, both of which my moon has.

  2. The claim that most moons aren't going to have major amounts of liquid surface also falls flat in that I've seen numerous sources saying that if a moon of a gas giant were to migrate inward, it would be a so called water world (sources at the very end, and I'll provide more if needed).

  3. The fact that bowlturner cites Titan as having ice under its surface, yet neglecting to mention the fact that much of this ice would melt and populate the surface of Titan with much more water were it to heat up is also a point of contention.

  4. The answer provided by bowlturner does not provide enough qualifiers under the "hard-science" tag, and therefore does not answer my question.

In summary, not only is the answer given not definitive for my question, much of what is said is actually not true for all or most cases.

Question Based Proofs

  1. My question pertains to any liquid, and not necessarily just water. This allows for different densities, freezing and boiling points, heat absorption and dispersion rate, and many other factors as long as they would be liquid on the surface.

  2. Green asked a question wondering whether a watery world could and would be tidal locked, whereas my question asks specifically how to prevent tidal locking with any liquid in high quantities under specified parameters for a terrestrial based moon.


Background:

I've been researching tidal locking like no other, and I've seen ways of getting around it, and pretty much all of them have been well explained, except for one.

I've seen very very vague comments alluding to keeping a world from tidal locking if it's covered in liquid water (or I'm assuming any liquid). After the first one, I thought it was just a fluke or something, and then I saw one or two more, and now I'm very intrigued as to whether this could be a viable natural way of stopping tidal locking (as long as the liquid stays).

Now it may be specifically because of an atmosphere that this would occur, but I really don't know. I know that in the case of an atmosphere, it has something to do with angular momentum and heat lagging behind the time of when it heats the ground vs the atmosphere or something along those lines, and I'm curious if this could be a similar case that is multiplied more for a mostly liquid surface.

THE QUESTION:

Could you stop or reverse tidal locking on the surface (or mantle) of a terrestrial based moon (see info about pertaining system) by having a mostly liquid (only one main piece of land mostly used as a way to test the tidal lock) covered world? If yes, how much liquid would be needed, and would said liquid need to be of a specific density or viscosity to even be possible? And I would appreciate a "why" in any given answers (preferably with linked articles or other proofs).

Also, please note that this is a theoretical moon that could have originated any natural way: a former rogue planet, a former inner planet, a naturally formed moon, a leftover body from colliding with another body, or any other natural possible means of getting a moon around a gas giant; I clarified this to include objects that may have had higher chances of having large amounts of surface water to start.

Info about the pertaining system:

The moon orbiting the gas giant in my situation has no satellites of its own, and the primary (gas giant) is around 1-12.5 Jovian masses. My moon is near terrestrial sized (0.4-1.5 Earth masses and .6-2 Earth radii) with plate tectonics, a decent surface pressure due to atmosphere (maybe 0.5-2.5 bar; see source 4), an orbiting distance between .0067 au and .03 au, vulcanism (non-rampant), a substantial magnetosphere, appropriate escape velocity for near Earth habitability conditions (or for that of a liquid used in an answer), and a partridge in a pear tree.

IT DOESN'T MATTER HOW IT GOT THESE THINGS, IT JUST JUST MATTERS WHAT HAPPENS ONCE IT IS IN A STABLE ORBIT WITH TERRESTRIAL BASED CONDITIONS.

Temperature is whatever is needed to provide for necessary high volumes of liquid, and I would appreciate any answers specifying temperature, if it is a highly specific range within that the range of making a substance a liquid.

If any of those conditions are too limiting in determining things, just let me know. Also, if you need more information, I'd be happy to provide.


For anyone interested in other ways of preventing tidal locking, I'll list some here:

  1. Having an eccentric orbit that increases the body's chance of being caught in a higher spin orbit resonance (above tidal locking's 1:1 ratio of how many spins per orbits in the same time) such as Mercury's 3:2.

  2. Having a specific pressure atmosphere will allow for closer orbits than objects very thin or non-existent atmospheres that would tidal lock at the same distance (refer to: https://www.centauri-dreams.org/?p=32547)

  3. Being very misshaped while being able to retain being misshaped through tensile strength or other means similar to the moon Hyperion.

  4. Having multiple strong tidal forces acting upon a body at different distances, angles, and forces, or having negligible tidal forces acting on the body.

  5. Being a rogue ninja planet mo-fo whose world doesn't revolve around anyone or anything.

  6. The obvious one of artificial means.


Sources:

  1. Starting at 7:23 he mentions possible water worlds https://youtu.be/Evq7n2cCTlg

  2. The main post here: Habitable moon of a gas giant: working out the sizes and distances explains about water heavy worlds about 3/4 of the way down, and mentions an article as well.

  3. Also, here is an article linking how much water certain moons and bodies outside Earth have https://www.google.com/amp/s/amp.businessinsider.com/water-space-volume-planets-moons-2016-10, and I'm definitely not a astronomer, but I would assume that a terrestrial sized moon with these proportions (or possibly more due to atmosphere and higher escape velocity due to gravity) would have significantly more water.

  4. Second answer provides some numbers in regards to oxygen based survivable conditions with different pressures : https://space.stackexchange.com/questions/10895/maximum-survivable-atmospheric-pressure.

  5. A link exploring tidal locking not happening because of certain atmospheres at certain distances: http://physicsworld.com/cws/article/news/2015/jan/15/exoplanets-could-avoid-tidal-locking-if-they-have-atmospheres

Additional resources

I'm also providing any additional resources that I can find that may help others better find the answer to the question since I sometimes have a hard time understanding specific graphs and deeper astronomy or astrophysics based terms.

  1. A chart showing water states based on pressure. https://upload.wikimedia.org/wikipedia/commons/0/08/Phase_diagram_of_water.svg

TL;DR: How does little or lots of liquid affect tidal locking and why?

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  • $\begingroup$ Why would liquid water keep a body from becoming tidally locked? Tidal locking happens because of a differential gravitational field acting on an elastic object. Having liquid water on an object won't stop it from being tidally slowed. Read through the Wikipedia page on tidal locking. $\endgroup$ – Phiteros Oct 22 '17 at 2:01
  • $\begingroup$ @Phiteros I don't know if this changes your mind at all on tidal locking, but I've added a 5th source that explains how atmospheres can also mitigate tidal locking. Also, I believe I tried to read about what exactly causes tidal locking on Wikipedia before, and had a really hard time of it. $\endgroup$ – LanceLercher Oct 22 '17 at 2:15
  • $\begingroup$ From reading that article, it looks like their argument is that strong fluid currents at the surface could counteract some of the tidal torque. So you'd have to specify that you would have global currents that were very fast. $\endgroup$ – Phiteros Oct 22 '17 at 2:30
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Could you reverse tidal locking?

No. The only really practical way to "reverse" tidal locking on a long time scale is by an infusion of new angular momentum from outside the system; e.g., by an enormous impact event.

If the moon has very low dissipation, either because it is perfectly rigid or perfectly fluid, such that its long-term rotation is not affected by tidal effects, but the primary does not, then a moon may change from synchronously-rotating to non-synchronously rotating over time as tidal interactions change its distance from the primary. But in that case, you didn't really have a "tidal lock" in the first place--just a coincidence.

Could you stop or reverse tidal locking on the surface?

That depends on exactly what you mean. The fluid surface of a tidally-locked body can still flow freely, despite the synchronously-rotating state of the body as a whole. In certain cases, you may get super-rotation, such as happens in the upper atmosphere of Venus (although I'm not certain if that could happen with a liquid surface), where the fluid surface is most definitely not motionless with respect to the primary. Does that count as "reversing tidal locking on the surface"? What about regular ocean currents, without the need to be globally-coherent?

In either case, this would not result in moving the land at all. You wouldn't get super-rotation in the mantle, but you could certainly have mantle currents driven by internal heat driving the motions of crustal plates just like we have on Earth, independent of the body's global locked state. Most reasonable people would not count that as "reversing tidal lock". A sufficiently large tectonic event that significantly alters the internal mass distribution of the world, however, could result in a change to the equilibrium orientation of the body, allowing tidal torques to start rotating it again; the world would then wobble back and forth like a pendulum for a while before coming to a new steady state. Does that count as "reversing tidal locking"?

Could one prevent tidal locking by having a mostly liquid covered world?

That depends on just how much liquid you have, and how viscous it is. Tidal locking proceeds much more quickly when the world has a large dissipation factor--i.e., when it generates lots of heat when it deforms. A perfectly rigid body doesn't deform, so it doesn't lose any energy in deformation. A perfectly fluid body with zero viscosity doesn't lose any energy to internal friction when it deforms, so, like a perfectly rigid body, it will also never lock. A thin layer of liquid on top of a solid surface, however, will generally produce a lot of friction, and thus dissipate a lot of rotational energy, as it flows across that solid surface under the influence of tides that deform the shape of the water layer.

So, a world that is all liquid, or liquid for a very long way down before you get to the solid center, may indeed avoid tidal locking for a much longer time than a solid world of equivalent size. But a world with only a thin liquid layer will actually lock faster. If you have any amount of land sticking up above the surface, you are almost certainly in the latter regime--your liquid surface is helping, not hindering, the tidal-locking process. If super-rotation is possible in a dense liquid medium (as noted above, I'm not certain one way or the other about that), then it may indeed prevent perfect tidal locking, just as atmospheric super-rotation does, with an intermediate depth range that does not completely isolate the solid region from the surface flow. However, you're certainly unlikely to get that kind of super-rotation if there is any significant amount of land sticking up and messing up the circulation patterns.

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  • $\begingroup$ Thank you so much for the answer! As I've been told previously, comments aren't the place for discussion, so it may be advantageous for me to start a chat in the near future based on those questions you asked of me. (That is if I even can.) $\endgroup$ – LanceLercher Oct 22 '17 at 6:18
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Even with the long explanations and specifications, it is not completely clear what you want.

Tidal locking can be disrupted by either changing the orbital speed of the moon, changing the rotational speed of the moon, or altering the orbital distance of the moon.

These can be altered by changes on the moon, or by changes on the body it orbits, or by proximity of other celestial bodies (a rogue planet, for instance, in a very eccentric orbit that passes by every three or four centuries).

Changes in the rotational speed of the planet can be altered by a change in its diameter (a spinning figure skater that spins faster by bringing her arms in). Perhaps a liquid that either expands or contracts by an extreme temperature change, or is expelled into space by some disruption or collision with an asteroid or other. Perhaps changes in density caused as a result of a chemical reaction, perhaps an intermingling of chemicals on the surface with others formerly locked in the core.

Changing the orbit could be as a result of some cataclysmic event of the planet - parts of it cleaved off or a large body captured by the planet, changing its gravitational pull.

If any of these strike your fancy, then perhaps someone can do the math. But perhaps you might want to select which method of disrupting the tidal lock you might prefer - orbit, spin, planetary change, or cosmic interloper.

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  • $\begingroup$ The only reason I've made this post ten times longer than it needed to be (which probably cluttered it more than necessary) is because no matter what I did, people persisted to call my previous version a duplicate of the afore mentioned post among other things. $\endgroup$ – LanceLercher Oct 22 '17 at 5:49
  • $\begingroup$ Thank you for your answer! I think I may ask a separate question that delves deeper into one of those scenarios in the near future. $\endgroup$ – LanceLercher Oct 22 '17 at 6:16

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