Imagine for a moment that Europa is not frozen solid (at least on the surface).

Would the fact that it is tidally locked to Jupiter mean that the water would be stagnate? So there would be no tides such as are caused by the rotation of the moon on earth's ocean?

I am sure Ganymede and Io would cause tides, but the question we are trying to answer is if a water planet tidally locked to another planet would have tides.

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    $\begingroup$ The main cause of waves is wind. Tides are caused by the gravity of the moon. Did you mean "tides" instead of "waves". $\endgroup$
    – James K
    Jun 19, 2021 at 16:54
  • $\begingroup$ Yes, I did not know the difference. Editing my question for clarity. Thank you for pointing this out. $\endgroup$
    – Bookaholic
    Jun 19, 2021 at 17:15
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    $\begingroup$ This might help geo.brown.edu/research/Milliken/GEOL0810_files/… $\endgroup$ Jun 19, 2021 at 18:20
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    $\begingroup$ Europa is too small to have a liquid water surface. Without its protective ice layer, the water would boil away. According to this page from Vanderbilt University, "a planet can hold onto its atmosphere if the escape velocity is about 4-6 times greater than the average kinetic velocity". But at 0°C, the mean speed of water vapor molecules is ~566.6 m/s, and the escape velocity at the surface of Europa is only 2025 m/s. $\endgroup$
    – PM 2Ring
    Jun 19, 2021 at 22:18

1 Answer 1


If Europa was the only large moon orbiting Jupiter then it wouldn't have tides, or, more accurately, it would have a permanent tidal bulge and no moving tides, so it depends on what you call a tide. A permanent tide is still a tide IMHO. There's still a tidal force creating a bulge.

It also doesn't have to have a liquid surface. Land tides or crustal tides aren't as apparent or as high, but they still happen. In fact, on a water world, tides would be hard to see. It's the combination of large bodies of water and more fixed land that makes the tides so visibly apparent.

Tides can move on a tidally locked body in a one large moon system if the orbit has some eccentricity. Eccentricity creates libration, so from the planet's point of view, the side of the moon facing the planet shifts back and forth a little (like our moon does), and from the moon's surface, the planet moves back and forth in the sky and as it moves the tides follow. In Europa's case, it's orbit is nearly circular so it wouldn't have moving tides.

Unlike Earth's tides which move around the planet, mostly following Earth's rotation, On a tidally locked, eccentric orbit moon, tides would move back and forth.

This happens on the lakes on Titan.


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