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USA: The Hubble Telescope has identified evidence of a massive saltwater ocean beneath the icy crust of our solar system's largest moon.
NASA scientists estimated the alien sea is 60 miles deep – 10 times deeper than Earth's oceans – and buried under a 95-mile crust of ice.
“This discovery marks a significant milestone, highlighting what only Hubble can accomplish,” said John Grunsfeld, associate administrator 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 only moon in the solar system to have its own magnetic field.
Space scientists used Hubble to look at the moon's aurora - ribbons of glowing, electrified gas which circle its north and south poles.
The aurorae are tugged around by Jupiter's own huge magnetic field.
Using Hubble's super-sensitive lenses, scientists watched the aurorae “rocking” back and forth under the force of Jupiter's magnetism.
They noticed the aurorae did not move as much as expected, suggesting an ocean was exerting its own magnetic pull.
"If you know the magnetic field, then you know something about the moon’s interior," said Joachim Saur from the University of Cologne in Germany, who first suggested using Hubble to learn about the moon.