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The top picture shows the icy surface of Europa. The icy surface might have a large ocean under it, inside of Europa. The bottom picture shows what the inside of Europa might be like. The blue is the possible ocean.
Click on image for full size
Images courtesy of NASA/JPL/ASU.

The Icy Galilean Moons of Jupiter

Jupiter has four big moons and a bunch of smaller ones. Three of the big moons - Europa, Ganymede, and Callisto - are covered with ice. That makes them a lot like Earth's frozen polar regions in some ways.

The surface of each of these moons is covered with ice. That doesn't mean all of the water in these moons is frozen. Scientists think these moons, especially Europa, might have salty oceans under their icy surfaces. Some places near Earth's poles have water under ice. Sea ice near the North Pole floats on top of the Arctic Ocean. There are also lakes in Antarctica thousands of meters beneath the polar ice sheet.

Water is a key ingredient for life. If there are oceans under the ice of Jupiter's moons, could there be life in those oceans? Astrobiologists are especially interested in Europa. Europa is hot inside. That's because it gets pulled and stretched by the gravity of Jupiter and the other moons. The same thing happens to Io. Io has lots of volcanoes because of this heat. Does Europa have volcanoes under its ice? Nobody knows for sure. If it does, it would be a lot like the hot water vents on the floor of the ocean on Earth. Those hot water vents have lots of living creatures around them. Could there be living creatures around hot vents under the ice on Europa?

Last modified August 3, 2009 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA