Mercury found to be tectonically active

Re:Mercury found to be tectonically active by mafribe on Tuesday September 27, 2016 @04:29AM (#12588137)

Io, Jupiter's innermost moon and the most volcanically active body in the solar system, is interesting because its source of heat is believed to be tidal heating: Jupiter's gravity pulls Io inwards while Jupiter's other moons pull Io outwards. This leads to a weird, eccentric orbit, which in turn means changing levels and directions of gravity leading to movement of Io's mass, e.g. molten rock under the surface. This causes friction that heats Io, whence volcanism.

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

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Re:Mercury found to be tectonically active by yathern on Tuesday September 27, 2016 @10:11AM (#12589680)

I'm no physicist, but I'm curious where the heat comes from, thermondynamically speaking. Does this changing level of gravity gradually sap the speed of Io?

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Re:Mercury found to be tectonically active by T-hawk on Tuesday September 27, 2016 @11:05AM (#12590118)

Yes. It comes from the orbital kinetic energy of Io and the other moons.

The same happens in the Earth-Moon system. The Moon causes tides on Earth's oceans, which increase friction between water and land and therefore produce heat. Thermodynamically speaking, that heat comes from the Moon's orbital momentum, as it recedes from Earth and slows in its orbit.

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Re:Mercury found to be tectonically active by mafribe on Tuesday September 27, 2016 @12:06PM (#12590632)

Earth has also got a small bit of tidal movement of the crust, but not remotely as much as Io. There there is a theory that tidal movement of the Earth's crust is one (of many) factors that can trigger earthquakes.

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Re:Mercury found to be tectonically active by dspillett on Tuesday September 27, 2016 @12:22PM (#12590780)

>(of many) factors that can trigger earthquakes.

Or slowly feed in energy that is stored and released when something else pushes the system far enough out of equilibrium that a quake happens.

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Re:Mercury found to be tectonically active by T-hawk on Tuesday September 27, 2016 @12:46PM (#12590971)

"Feed in energy" - that energy has to come from somewhere. The point of this subthread is where does that energy come from thermodynamically? The answer is orbital or rotational kinetic energy via tidal forces, which of course do affect both crust and water.

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Re:Mercury found to be tectonically active by mafribe on Tuesday September 27, 2016 @12:58PM (#12591054)

Yes, but different celestial bodies get there energy from different sources. For the earth it's mostly radioactive decay in the core of the planet.

In others, like Io, it's believed to be mostly tidal friction.

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Re:Mercury found to be tectonically active by parr0t on Tuesday September 27, 2016 @05:17AM (#12588276)

Fascinating. Thanks for the link.

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