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        Washington: NASA has announced evidence that Jupiter's largest moon, Ganymede, has a saltwater ocean under its icy surface. The ocean seems to have more water than all the water on Earth's surface, according to new Hubble observation.

         New Hubble observations of Ganymede's magnetic field strongly suggest that the moon, which is the largest in our whole solar system, is home to a subsurface ocean.

        Scientists estimate the ocean is 95 kilometers thick, which is about 10 times deeper than Earth's oceans. But unlike our salty waters, Ganymede's ocean is buried under 150 kilometers of ice.

         While scientists have speculated(推测) since 1970s about the presence of an ocean on Ganymede—the largest moon in our solar system—until now the only observational evidence came from a brief flyby by the Galileo spacecraft, which didn't observe the moon long enough to confirm a liquid ocean.

         This discovery marks an important milestone, highlighting what only Hubble can accomplish. In its 25 years in orbit, Hubble has made many scientific discoveries in our own solar system. A deep ocean under the icy surface of Ganymede opens up further exciting possibilities for life beyond Earth.

        Scientists have already confirmed the existence of an ocean on Europe, another moon orbiting Jupiter, and NASA has announced plans to send an unmanned mission there searching for the life that might come with liquid water.

       Hubble is a telescope that orbits Earth, but because of its impressive gravitational analyses it can be used to study the inside of far distant planets. Using these same principles, scientists could theoretically detect oceans on distant planets as well.