Tidal Heating

Tidal Heating in Spore

If you ever come across a moon that is very far the sun yet it appears rather warm, maybe even hospitable then you can expect that there is probably some sort of tidal heating going on. Tidal Heating is not enough to support life, but it does increase its chances.

What is Tidal Heating?

The moons of the gas giant Jupiter are far away from the sun, yet they are much warmer than they should be. This is mostly caused by tidal heating and it’s only possible when a moon is paired with a much larger parent planet and in resonance with other other moons (in this case, Ganymede and Europa). To try and explain what tidal heating is, lets use a soft rubber ball as an example. When you squish the ball and then let it relax, you are mimicking the effect of Jupiter’s gravity on some of its inner moons. If you squish and relax long enough, the ball will begin to heat up because of friction. Jupiter also causes this sort of distortion, but on a larger scale and with gravity instead of a physical interaction. These moons are experiencing a sort of tug of war between the gravity of Jupiter and the other nearby moons. The friction causes enough heat to make some of the moons much warmer than they should be.

Moons experiencing Tidal Heating

Io
Inner most Galilean moon of Jupiter and receives the brunt of the planet’s gravitational forces. This moon has the most volcanic activity of any body in our solar system and it’s almost entirely due to the huge amount of friction it feels. Rough estimates show the the moon bulging as much as 100 meters because of tidal forces. But because of the intense volcanic activity, chances of life here are extremely slim!

Europa
This moon is considered by some scientists to have the greatest chance of life of any bodies in our solar system (besides earth!). If you look at its surface, it looks like a giant ball of ice. But there is tidal heating going and evidence that water sometimes spills out onto the surface. These observations along with the known effect of Tidal Heating lead many to believe that there is a very deep ocean underneath the icy surface, with the possibility of life near deep sea vents. It’s far too little energy to have any aquatic life as we know it (ie. fish), but there could very well be microscopic life.

Ganymede
The largest moon in our solar system (slightly larger than Titan and larger than the planet mercury)under goes Tidal heating and it also has retained a fair amount of heat because of its large size. It may have a deep underwater ocean, but the ice pack is likely much larger than that of Europa.