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For use with Chapter 25
Electromagnetic Induction

Evidence for Oceans on Europa
Posted February 1, 2000

NASA's Galileo spacecraft orbited and studied Jupiter and its satellites for two years. Upon completion of its primary mission, Galileo's tour of the Jovian system was extended and includes further observation of Jupiter's moon, Europa. During a recent flyby of that moon, new evidence was gathered that an ocean of liquid water exists beneath the massive ice surface.

Water is abundant on Europa. In fact, there is more water on Europa than the total amount of water found on Earth. But so far only the surface of solid ice has been observed. The appearance of Europa's surface led to the hypothesis that a layer of liquid water existed below the ice layer, but there was no supporting evidenceŠuntil now.

Europa experiences a change in direction of Jupiter's magnetic field every 5 1/2 hours. A change in a magnetic field generates an electric current in a conductor. This current, in turn, can produce its own magnetic field. On past flybys of Europa, Galileo detected a magnetic north pole. However, on this most recent visit, it discovered that the north pole was reversing direction every 5 1/2 hoursŠright in synch with Jupiter's changing magnetic field.

Ice and pure water are poor conductors of electricity. However, dissolved salts make water a better conductor of electricity. NASA scientists say that an ocean containing dissolved salts beneath the layer of ice could explain the observed changes in Europa's magnetic north pole.

The composition and extremes in pressure, temperature, and magnetic field on Jupiter are hostile to life as we know it. But, based on the discovery of organisms thriving near hydrothermal vents in Earth's oceans, scientists have discussed the possibility that organisms could survive on Europa. Other moons of Jupiter also may offer similar conditions that support life.

The extended Galileo mission was scheduled to end in January 2000. NASA is currently considering another extension, the Galileo Millenium Mission that would include flybys of Jupiter's moons, Io and Ganymede, and a joint observation of Jupiter with the Cassini spacecraft.

Activity
Research the history of the Galileo spacecraft and the data it has provided. Develop a timeline detailing the probe's mission.

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