5 Unsolved Mysteries of Our Solar System's Moons

5 Unsolved Mysteries of Our Solar System's Moons

What are those strange lines on Europa? Why do Io's volcanoes seem to be misplaced? What is the origin of that colossal ridge on Iapetus?

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The solar system is so full of odd stuff like that and then you move to other solar systems where stuff just becomes even weirder... I hope I live to see the answers of some of these mysteries.

Awesome article, I knew about Miranda and obviously Titan but all other stuff was new to me.

Halyah:
The solar system is so full of odd stuff like that and then you move to other solar systems where stuff just becomes even weirder... I hope I live to see the answers of some of these mysteries.

Gotta agree with you there! We've barely scratched the surface. Heck, most of these moons were discovered in the past 10 years or so!

Nimcha:
Awesome article, I knew about Miranda and obviously Titan but all other stuff was new to me.

Cheers! Glad you could learn a thing or two. I think everyone should challenge themselves to learn something new every day.

Rhykker:

Halyah:
The solar system is so full of odd stuff like that and then you move to other solar systems where stuff just becomes even weirder... I hope I live to see the answers of some of these mysteries.

Gotta agree with you there! We've barely scratched the surface. Heck, most of these moons were discovered in the past 10 years or so!

Some of these discoveries makes me wonder if the universe is just dicking with us on purpouse, but hey if it keeps giving us questions, we'll keep looking for answers. So bring on more mysteries! But also answers because I really wanna know how the heck that one moon managed to get such a weird ridge across the middle. It looks like someone took a blowtorch to two halves of a sphere to merge them together.

Halyah:

Rhykker:

Halyah:
The solar system is so full of odd stuff like that and then you move to other solar systems where stuff just becomes even weirder... I hope I live to see the answers of some of these mysteries.

Gotta agree with you there! We've barely scratched the surface. Heck, most of these moons were discovered in the past 10 years or so!

Some of these discoveries makes me wonder if the universe is just dicking with us on purpouse, but hey if it keeps giving us questions, we'll keep looking for answers. So bring on more mysteries! But also answers because I really wanna know how the heck that one moon managed to get such a weird ridge across the middle. It looks like someone took a blowtorch to two halves of a sphere to merge them together.

If you think the moons are trying to screw with your mind, ask Saturn about its hexagon-shaped storm sometime.

The Rogue Wolf:

If you think the moons are trying to screw with your mind, ask Saturn about its hexagon-shaped storm sometime.

I knew about that one already. It's pretty interesting how that sort of shape showed up in a storm rather than in a crystaline structure where you'd expect it... The universe is weird!

Halyah:
*snip*

So bring on more mysteries! But also answers because I really wanna know how the heck that one moon managed to get such a weird ridge across the middle. It looks like someone took a blowtorch to two halves of a sphere to merge them together.

Hahah, yeah, Universe. Stop being an episode of LOST! We need some answers, too!

Europa scientist here! Let's take a look-see, shall we?

Jupiter's fourth largest moon, Europa is famous for being covered in water ice - and for the possibility of the liquid ocean that may lie beneath it. But beyond that, its surface is scarred with intersecting lines - cracks and dark streaks that span the entire globe and can reach 20 km in width.

Actually, the liquid ocean most definitely exists beneath it, as evinced by the induced magnetic field measured by the Galileo probe, shown to be due to the flow of ions in solution less than 100 km from Europa's surface. Most computer models that take into account the heat generated by tidal flexure suggest that Europa's ice shell is approximately 20 km thick; including my own work on the subject.

The origin of these lines is unclear, but the most likely hypothesis states that they are the result of warm ice erupting onto the surface, not unlike the way ocean ridges open up on Earth and spew out lava.

This is most likely incorrect. Europa in its current state (ever since it's been locked in orbital resonance with Ganymede and Io) does not have enough ocean pressure for extrusive cryovolcanism (i.e. water eruptions) to take place. This is in contrast to a satellite like Enceladus, whose ice shell is thick enough that the water underneath is overpressurized enough, due to ice's expansion as it freezes, to have gigantic water eruptions centered around its south pole. A model one of my friends is working on is investigating whether intrusive cryovolcanism may form Europa's ridges, in which water rises part way through the shell, freezes and expands there, and then buckles it. Results look promising.

agreen15:
Europa scientist here! Let's take a look-see, shall we?

Jupiter's fourth largest moon, Europa is famous for being covered in water ice - and for the possibility of the liquid ocean that may lie beneath it. But beyond that, its surface is scarred with intersecting lines - cracks and dark streaks that span the entire globe and can reach 20 km in width.

Actually, the liquid ocean most definitely exists beneath it, as evinced by the induced magnetic field measured by the Galileo probe, shown to be due to the flow of ions in solution less than 100 km from Europa's surface. Most computer models that take into account the heat generated by tidal flexure suggest that Europa's ice shell is approximately 20 km thick; including my own work on the subject.

The origin of these lines is unclear, but the most likely hypothesis states that they are the result of warm ice erupting onto the surface, not unlike the way ocean ridges open up on Earth and spew out lava.

This is most likely incorrect. Europa in its current state (ever since it's been locked in orbital resonance with Ganymede and Io) does not have enough ocean pressure for extrusive cryovolcanism (i.e. water eruptions) to take place. This is in contrast to a satellite like Enceladus, whose ice shell is thick enough that the water underneath is overpressurized enough, due to ice's expansion as it freezes, to have gigantic water eruptions centered around its south pole. A model one of my friends is working on is investigating whether intrusive cryovolcanism may form Europa's ridges, in which water rises part way through the shell, freezes and expands there, and then buckles it. Results look promising.

Fascinating. Can that explain why the lines criss-cross? Appreciate your insight!

The criss-crossing lineae are probably best explained, as you said, by the ice shell's non-synchronous rotation. There's actually been a few fascinating studies on what the concurrent tidal stresses and non-synchronous rotation put Europa's shell through. The principal direction of stress on Europa's shell is in constant flux, which causes fractures to form frequently in any direction, often overwriting earlier landmarks and fractures. I've seen some really nifty animations of what this evolving stress field looks like, but alas, I cannot dig them up. These features on Europa, however, called cycloids, clearly illustrate the effects of tidal stresses on a freely rotating spherical surface:

image

The cycloids can be seen in this picture as parallel bands that form prominent arcuate curves. I don't know too much about the specific mechanisms that form them, as my specialty is in modeling the thermodynamics of the entire ice shell rather than the formation of surface features, but I think they propagate along the principal direction of tidal stress as it changes over time.

agreen15:
*snip*

Do you have any animated thermodynamic models? (I know not to expect awesome sci-fi CGI; I've worked in research labs) I'd love to see any examples of your research.

Not being scientifically inclined I can offer no other insight besides marveling at what even smarter people don't quite understand yet.

But man it makes me wish we could fly into space and do all sorts of star trek science fictiony things to find out.

 

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