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Science, Evolution, and Creationism, by the National Academies, focuses on teaching evolution in today's classrooms. Check out the other publications in our online store.

Exploratour - Does Europa have an Ocean?

This image shows the Earth and the moon, and the bulges produced on each side from the tides.
Click on image for full size

Reasons that planetary bodies are warm include

  • 1.) leftover heat from it's formation
  • 2.) radioactive material found in the body
  • 3.) outside forces on the body as a whole, such as those which cause tides
  • 4.) warming by the sun

Reason #3 applies to Europa. An example of what happens is shown in this drawing of the Earth and Moon. In this picture, the gravitational force of the Earth is pulling on the Moon, and the gravitational force of the Moon is pulling on the Earth. The Moon pulls more strongly on the side of the Earth facing the Moon than on the side facing away from the Moon. Because planets are not perfectly rigid, they change their shape when they are pulled this way.

In the case of Europa, the push-me, pull-me effect is caused by the pull of Jupiter on one side, and the other moons of Jupiter on the other side. (Europa is an inside moon). The volcanism of Jupiter's moon Io is caused by the very same effect.

If a body is very rigid or is not held together well, instead of getting pushed and pulled out of shape, the tidal forces can actually tear the body in half, as with comet Shoemaker-Levy 9.

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF