Europa May Have Plate Tectonics

[tentacle]

http://www.space.com/27059-jupiter-moon-europa-plate-tectonics.html

 

Very interesting article. I would like to see your comments. How did Europa formed in the first place and how is this possible?

 

[Acme]

http://www.space.com/27059-jupiter-moon-europa-plate-tectonics.html

 

Very interesting article. I would like to see your comments. How did Europa formed in the first place and how is this possible?

As to how it's possible, the article explains.

...He and Prokter said Europa likely has a system of cold, brittle plates moving around above convecting warmer ice. The mechanisms behind Europan plate tectonics are unclear at the moment, Kattenhorn said, stressing the need for modeling work. But tidal heating generated by the tug of Jupiter's immense gravity, the same phenomenon that keeps Europa's interior ocean from freezing up, may be one of the ultimate drivers, he added. ...

They also make clear in the above that while tidal heating is a likely possibility, further work is necessary to pin down the mechanism.

 

Here's a bit on the formation of moon-ring systems from Wiki: >>Formation and evolution of the Solar System: Moon-ring systems

[Ophiolite]

Formation of Europa

 

While more than one hypothesis has been put forward for the origin of Europa and the other Galilean satellites, formation in Jupiter's accretion disc during its formation is best supported by the evidence. This would be equivalent to the formation of the planets in the solar system, with Jupiter playing the role of the sun, the whole applied on a smaller scale. Canup and Ward, two well established planetary scientists say this in their introduction to a chapter on Europa's origin in the book Europa from the University of Arizona Press:

 

Europa is believed to have formed near the very end of Jupiter’s own accretion, within a circumplanetary disk of gas and solid particles. We review the formation of the Galilean satellites in the context of current constraints and understanding of giant planet formation, focusing on recent models of satellite growth within a circumjovian accretion disk produced during the final stages of gas inflow to Jupiter. In such a disk, the Galilean satellites would have accreted slowly, in more than10⁵yr, and in a low pressure, low gas density environment. Gravitational interactions between the satellites and the gas disk lead to inward orbital migration and loss of satellites to Jupiter. Such effects tend to select for a maximum satellite mass and a common total satellite system mass compared to the planet’s mass. One implication is that multiple satellite systems may have formed and been lost during the final stages of Jupiter’s growth, with the Galilean satellites being the last generation that survived as gas inflow to Jupiter ended.

Plate Tectonics

I am very uncomfortable with¹ calling this plate tectonics. Yes, there appear to be plates; yes there appear to be tectonic movements and structures associated with these plates, but:

 

a) The relative size of the plates appears to be different to those on Earth

b) Convective flow is in a liquid, not a solid

c) and consequently the time scale is quite different.

d) There do not to appear to be the equivalents of continental and oceanic crust that are such important aspects of terrestrial plate tectonics.

e) The diversity of rock types and the complexities this introduces in terms of magmatic genesis, initiation of subduction, diaparism, etc are absent from Europa.

 

If we seriously wish to call this plate tectonics then the stagnant lid/single plate tectonics thought to dominate Mars and Venus needs to be called plate tectonics too.

 

And while we are at it, I would challenge the impression created by the article that "conventional plate tectonics" is thought to be absent form those two planets. Several workers have presented arguments for plate tectonics having been active on both, and in the case of Venus, very recently.

 

So, to be clear, I am not questioning the findings. I am questioning the sloppy use of the term "plate tectonics" perhaps in an effort to attract media attention and grant money.

 

 

1. British understatement for bollocks.

Edited September 10, 2014 by Ophiolite

[MigL]

Always thought plate tectonics meant a liquid core on which solid plates 'float'.

Mars has little if any molten core left, so the solid surface doesn't 'float'.

Europa has a single level solid surface, so sections of the solid surface plates don't rise over or descend beneath other plates. But they do crush into each other somewhat like ice floes in the Arctic. Does that mean they cannot be called plate tectonics which has a very specific meaning ?

 

On a related note, is it possible for Europa to be liquid all the way to the centre ? It would need to be composed of mostly one thing and be a certain size, but is it possible ?

[arc]

http://www.space.com/27059-jupiter-moon-europa-plate-tectonics.html

 

Very interesting article. I would like to see your comments. How did Europa formed in the first place and how is this possible?

 

 

If that can be considered plate tectonics then what would you call drift ice, pack ice and its many related structures such as pressure ridges?

 

http://en.wikipedia.org/wiki/Pressure_ridge_(ice)

 

Image by Lusilier and provided through Wikimedia Commons.

The blocks making up pressure ridges are mostly from the thinner ice floe involved in the interaction, but it can also include pieces from the other floe if it is not too thick. In the summer, the ridge can undergo a significant amount of weathering, which turns it into a smooth hill.

http://en.wikipedia.org/wiki/Sea_ice

Image by Lusilier and provided through Wikimedia Commons.

 

Though they share similar terminology and maybe even some of the same mechanics they are vastly more different than the same.

 

I for one would want plate tectonics to refer to processes that result in the many surface and subsurface structures like mountains, basins, valleys and extensional features like the Basin and Range area. And also the very many types of materials that result from those processes, tectonics on earth are a veritable factory where all of the terrestrial building materials are made or processed. That ice on Europa seems rather two dimensional, rather uniform when compared to what terrestrial tectonics can deliver in terms of grandeur.

 

Its just ice after all.

[Ophiolite]

Always thought plate tectonics meant a liquid core on which solid plates 'float'.

You are mistaken, holding a common, but incorrect belief. Plate tectonics arises through convection in the solid mantle. Solids can and do flow - if any one wishes I can go into a little detail on the mechanisms involved.

 

The convection may arise as a consequence of plumes of mantle material rising from the core/mantle interface. These would occur whether or not the outer core was liquid, though I think their strength would drop off rapidly after the core had solidified, since the temperature contrast would drop - no convection in core to maintain the differential.

 

However, the role of the core in initiating, or maintaining plate tectonics is hotly debated. It is certainly not the only factor and may be a minor factor.

 

 

Mars has little if any molten core left, so the solid surface doesn't 'float'.

As I said above, this does not work. As I noted in my initial post, most researchers think that Mars and Venus experience stagnant lid tectonics. In these, convection still occurs in their solid mantles, but only in the lower mantle. The upper mantle is too viscous and internal heat is transmitted via conduction.

 

Europa has a single level solid surface, so sections of the solid surface plates don't rise over or descend beneath other plates. But they do crush into each other somewhat like ice floes in the Arctic. Does that mean they cannot be called plate tectonics which has a very specific meaning ?

That is my contention. Please note that this is an opinion, but it is the opinion of a keen amateur, with professional training who has carried out extensive reading on the subject. The use of the term appears to me to be more about PR than science.

 

Which has more appeal?

Scientists discover surface of Europa moves around just like ice floes in the Arctic (which was bloody obvious was likely the case ever since we saw the Voyager photographs 35 years ago).

Or,

Scientists discover plate tectonics on Europa.

 

On a related note, is it possible for Europa to be liquid all the way to the centre ? It would need to be composed of mostly one thing and be a certain size, but is it possible ?

No, models of its interior preclude that possibility.

 

Again, I think this is important and interesting news, whose significance is actually diminished by misusing established terminology. I would have no problem if someone were to write a paper redefining plate tectonics to incorporate the following types:

a) Terrestrial style 'deep penetrating' plate tectonics.

b) Europa style 'shallow penetrating' plate tectonics

c) Martian style stagnant lid 'plate tectonics'

d) Venusian styles stagnant lid with periodic convective crustal overturn plate tectonics

e) etc.

[MigL]

Thanks for the clarification, Ophiolite.

[tentacle]

What about Titan plate tectonics?

[Ophiolite]

Probably not. Here is the latest refereed paper I can find on Titan tectonics:

 

Solomonidou, A. et al Morphotectonic Features on Titan and Their Possible Origin Planetary and Space Science Volume 77 March 2013, Pages 104–117

 

Abstract

Spectro-imaging and radar measurements by the Cassini–Huygens mission suggest that some of the Saturnian satellites may be geologically active and could support tectonic processes. In particular Titan, Saturn's largest moon, possesses a complex and dynamic geology as witnessed by its varied surface morphology resulting from aeolian, fluvial, and possibly tectonic and endogenous cryovolcanic processes. The Synthetic Aperture Radar (SAR) instrument on board Cassini spacecraft, indicates the possibility for morphotectonic features on Titan's surface such as mountains, ridges, faults and canyons. The mechanisms that formed these morphotectonic structures are still unclear since ensuing processes, such as erosion may have modified or partially obscured them. Due to the limitations of Cassini–Huygens in the acquisition of in situ measurements or samples relevant to geotectonics processes and the lack of high spatial resolution imaging, we do not have precise enough data of the morphology and topography of Titan. However we suggest that contractional tectonism followed by atmospheric modifications has resulted in the observed morphotectonic features. To test the possibility of morphotectonics on Titan, we provide in this work a comparative study between Cassini observations of the satellite versus terrestrial tectonic systems and infer suggestions for possible formation mechanisms.