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

Each of these moons has some rocky material inside. However, they all have lots of ice in them too. The surface of each moon is also covered with ice. That doesn't mean that 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 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?

These icy moons are like Earth's poles in one more way. If you could visit these moons, you might see the aurora - which we call the Northern Lights or Southern Lights on Earth. Scientists have spotted aurora on Ganymede. They think Europa and Callisto might also have beautiful auroral light shows too.

Last modified August 3, 2009 by Randy Russell.

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Galilean Satellites

The Galilean satellites are the 4 major moons of Jupiter, Io, Europa, Ganymede, and Callisto. In this picture, Io, and Io’s surface, are shown on the left-most end, then Europa, and its surface, then Ganymede,...more

Europa

Europa was first discovered by Galileo in 1610, making it one of the Galilean Satellites. It is Jupiter's 4th largest moon, 670,900 km from Jupiter. With a diameter that is about half the distance across...more

Callisto

Callisto was first discovered by Galileo in 1610, making it one of the Galilean Satellites. Of the 60 moons it is the 8th closest to Jupiter, with a standoff distance of 1,070,000 km. It is the 2nd largest...more

Does Europa Have an Ocean?

The surface of Europa shows many signs of that there may be an ocean under the surface: * flooded terrain * 'freckles' * rafting * 'mushy' craters, and * spreading centers. Taken together, these pieces...more

Sea Ice in the Arctic and Antarctic

Sea ice is frozen seawater. It can be several meters thick and it moves over time. Although the salts in the seawater do not freeze, pockets of concentrated salty water become trapped in the sea ice when...more

Glaciers and Ice Sheets

For a glacier to develop, the amount of snow that falls must be more than the amount of snow that melts each year. This means that glaciers are only found in places where a large amount of snow falls each...more

Interior of Europa

The diagram to the left shows a cutaway of the possible interior structure of Europa. The composition of the icy moons is mostly ice, therefore there is probably a small core of some rocky material buried...more

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