Jupiter’s largest moon Ganymede said to have underground ocean

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Latest Hubble Telescope observations have more or less confirmed the existence of an underground ocean on Jupiter’s largest moon, Ganymede thereby broadening the hunt for places in the solar system where life might be able to exist.

Researchers revealed that the telescope spotted aurorae glowing above the moon’s icy surface. Aurorae, which NASA describes as “ribbons of glowing, hot electrified gas” can be seen in regions around the north and south poles of the moon. Because aurorae are controlled by a moon or a planet`s magnetic field, observing changes in their behavior can lead to better understanding of what exists under the crust.

“Since the 1970s, there were speculations and models that Ganymede could possess an ocean,” said Joachim Saur of the University of Cologne in Germany. “We do not have these ambiguities anymore.”

The latest findings from Hubble are the best evidence to date for the existence of an ocean on Ganymede.

Researchers found that Jupiter’s own magnetic field interacts with Ganymede’s, causing a rocking motion in the aurorae. This motion is reduced by magnetic friction applied by the presence of Ganymede’s underground ocean.

Scientists estimate the ocean is 60 miles (100 kilometers) thick — 10 times deeper than Earth’s oceans — and is buried under a 95-mile (150-kilometer) crust of mostly ice.

The new observations were done in ultraviolet light and could only be accomplished with a space telescope high above Earth’s atmosphere, which blocks most ultraviolet light.

“This discovery marks a significant milestone, highlighting what only Hubble can accomplish,” said John Grunsfeld, assistant administrator of NASA’s Science Mission Directorate at NASA Headquarters, Washington, D.C. “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.”