Searching for water, Galileo flies by Europa

Europa

January 4, 2000
Web posted at: 7:11 p.m. EST (0011 GMT)

(CNN) -- The Galileo spacecraft swooped close to Europa, searching for signs of a liquid ocean beneath the icy surface of the Jupiter moon, NASA's Jet Propulsion Laboratory said Tuesday.

The probe passed to within 351 kilometers (218 miles) of Europa, the sixth largest moon in the solar system. Scientists speculate it could hold more liquid water than Earth.

Instruments on the spacecraft observed magnetic fields and charged particles around Europa, looking for magnetic disturbances. A liquid ocean might generate electrical currents that would cause such disturbances, the Pasadena, California-based laboratory said in a statement.

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Europa's surface is mostly water ice, and there is strong evidence it may cover an ocean of slushy ice or even liquid water. The prospect of an ocean on Europa has intrigued scientists, as water is one of the ingredients essential for life.

Because Galileo passed behind Europa during the Monday flyby, its radio signal to Earth was temporarily blocked. NASA researchers took advantage of the situation to study how the radio signal changed as the spacecraft entered the "silent zone."

Such radio science experiments could provide information about Europa's ionosphere, the region of charged particles surrounding the moon, and any possible atmosphere.

After the Europa flyby, Galileo was to observe three smaller Jupiter moons, Amalthea, Thebe and Metis. Later it was to continue its study of the Jupiter moon Io, the most volcanic body in the solar system.

Galileo's onboard tape recorder is storing the data gathered during the observations. They will be transmitted to Earth over the coming weeks. The probe has orbited Jupiter and its moons since December 1995.

Italian astronomer Galileo Galilei discovered Europa on January 7, 1610.