Enceladus

[HopAlongBunny]

Further research is making Enceladus look like a prime candidate for life, or it's precursors.
Complex organic molecules are being spewed out from the plumes:

https://www.scientificamerican.com/a...oon-enceladus/

It might still be a long-shot for life (of some sort) but it is close enough to actually check

[Pannonian]

When did Enceladus overtake Europa in the possibility of life stakes? The description of Enceladus sounds like the description of Europa, and I'd have thought that Europa, being closer to the sun and being the moon of a bigger planet and thus being subject to bigger gravitational stresses, would have more geological activity and thus warmth.

[Crandar]

At first, I thought it was about earthquakes. I wasn't aware there was a Jupiter satellite called Enceladus.

[Husar]

When did Enceladus overtake Europa in the possibility of life stakes? The description of Enceladus sounds like the description of Europa, and I'd have thought that Europa, being closer to the sun and being the moon of a bigger planet and thus being subject to bigger gravitational stresses, would have more geological activity and thus warmth.

Why would it have bigger gravitational stresses in an orbit? Isn't the whole point of orbiting something that the gravitation of the object being orbited does not really matter? I mean, if it would, it wouldn't be an orbit but a fall, no? Maybe there's something I'm missing here.

[HopAlongBunny]

Maybe there's something I'm missing here.

Acceleration?
If different parts of the body are effected differently by the curvature of space-time then there acceleration is also affected.
This would result in stress upon each of the bodies with the smaller body experiencing the greater stress; the manifestation of those different stresses would also somewhat depend on the different composition of the mass influenced: gas, liquid, solid; the game of "push me pull you" gives you friction/heat
That is my amateur assessment; please correct me if I'm wrong...I really would like to know how this stuff works.

[Husar]

Acceleration?
If different parts of the body are effected differently by the curvature of space-time then there acceleration is also affected.
This would result in stress upon each of the bodies with the smaller body experiencing the greater stress; the manifestation of those different stresses would also somewhat depend on the different composition of the mass influenced: gas, liquid, solid; the game of "push me pull you" gives you friction/heat
That is my amateur assessment; please correct me if I'm wrong...I really would like to know how this stuff works.

That's an interesting idea, but I have two further questions/doubts:

1. Wouldn't all of the parts of the mass be affected to a more or less similar degree? Surely the parts closer to the big planet would be subjected to a bit more gravitation, but the difference would seem small, especially since the smaller object is usually some kind of solid rock. I don't think that's enough of a difference to cause a core to melt or whatever. The bigger body would even make the smaller one stop rotating like how the earth made the moon stop rotating. Additionally, earth went from really hot to a cold shell instead of getting heated up by the sun's gravitation somehow. The moon's gravitation affects some processes on earth (tides and possibly also in the core), but less so the other way around. Especially since the moon does not rotate around its own axis anymore.

2. The acceleration would not only depend on the size of the body that the small mass orbits, but also on the distance and the shape of the orbit. A low and less circular orbit should cause higher acceleration than a very high and very circle-shaped orbit around the same object, no?
The planet size would then be a more secondary factor. I'd expect the acceleration to be relatively low either way though, since a high acceleration would probably require a much stronger force than gravity, the weakest elementary force we know.

[Pannonian]

That's an interesting idea, but I have two further questions/doubts:

1. Wouldn't all of the parts of the mass be affected to a more or less similar degree? Surely the parts closer to the big planet would be subjected to a bit more gravitation, but the difference would seem small, especially since the smaller object is usually some kind of solid rock. I don't think that's enough of a difference to cause a core to melt or whatever. The bigger body would even make the smaller one stop rotating like how the earth made the moon stop rotating. Additionally, earth went from really hot to a cold shell instead of getting heated up by the sun's gravitation somehow. The moon's gravitation affects some processes on earth (tides and possibly also in the core), but less so the other way around. Especially since the moon does not rotate around its own axis anymore.

2. The acceleration would not only depend on the size of the body that the small mass orbits, but also on the distance and the shape of the orbit. A low and less circular orbit should cause higher acceleration than a very high and very circle-shaped orbit around the same object, no?
The planet size would then be a more secondary factor. I'd expect the acceleration to be relatively low either way though, since a high acceleration would probably require a much stronger force than gravity, the weakest elementary force we know.

I'm going by the stresses experienced by another of Jupiter's moons, Io. Also, can anyone answer my earlier question, why has Enceladus overtaken Europa in the possibility of life stakes? Both have similar descriptions, and Europa used to hold that title. What's the difference between the two?

[HopAlongBunny]

I found a better explanation at the ESA website:

https://www.esa.int/Our_Activities/S...lions_of_years



And a little summary on Tidal Heating from Wikipedia:

https://en.wikipedia.org/wiki/Tidal_heating

[Husar]

So it sounds like in this case, there is water flowing through porous rocks due to changes in gravity and that heats up the inside, or so is ESA's working theory since they don't seem to know either what else could cause it without the ability to look deeper inside it yet.

In the case of Io it's apparently also not the interactions with Jupiter that cause the tidal heating (it's in a tidal lock with Jupiter like our Luna is with Earth), but the gravity from the other moons, Europa and Ganymede, that causes the friction. This makes sense to me because the other moons would be passing by all the time and therefore change their position relative to Io, which Jupiter does not. Such a change in relative position would move things around, like how the moon moves water around here on Earth.
https://en.wikipedia.org/wiki/Io_(moon)#Tidal_heating

With Enceladus in contrast, it sounds like the elliptical path is what causes the flow, since the moon moves from stronger to weaker gravitation that could cause water inside to become compressed on the side facing the planet (higher gravitation) and then relax again and partially flow back to the other side due to internal pressure once the moon moves farther away from the planet again (lower gravitation). (This is what the ESA means with push pull motion I guess) In a rock this would probably cause nothing, but with a fluid flowing between porous rock, the movement would cause friction, or that's how I can make sense of the ESA idea.

Edit: Misread your wikipedia link at first, the deformation of the body due to varying gravitational force also or even mainly plays into it.