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An Underground Ocean on Jupiter’s Largest Moon

By David Reneke

An underground ocean has been discovered on Jupiter’s largest moon.

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NASA’s Hubble Space Telescope has the best evidence yet for an underground saltwater ocean on Ganymede, Jupiter’s largest moon. The subterranean ocean is thought to have more water than all of the water on the Earth’s surface.

“This discovery marks a significant milestone, highlighting what only Hubble can accomplish,” said John Grunsfeld of NASA’s Science Mission Directorate. “In its 25 years in orbit, Hubble has made many scientific discoveries in our own solar system. A deep ocean under the icy crust of Ganymede opens up further exciting possibilities for life beyond Earth.”

Ganymede is the largest moon in our solar system and the only moon with its own magnetic field. The magnetic field causes aurorae, which are ribbons of glowing, hot, electrified gas in regions circling the north and south poles of the moon. Because Ganymede is close to Jupiter, it is also embedded in Jupiter’s magnetic field. When Jupiter’s magnetic field changes, the aurorae on Ganymede also change, rocking back and forth.

By watching the rocking motion of the two aurorae, scientists were able to determine that a large amount of saltwater exists beneath Ganymede’s crust, affecting its magnetic field.

If a saltwater ocean is indeed present, Jupiter’s magnetic field would create a secondary magnetic field in the ocean that would counter it. This “magnetic friction” would...

The full text of this article can be purchased from Informit.