Scientists using . the Hubble Space Telescope have confirmed that the . Jupiter-orbiting moon Ganymede has an ocean beneath its icy . surface , raising the prospects for life , Nasa has revealed . The finding resolves a mystery about the largest moon in the . solar system after NASA 's now-defunct Galileo spacecraft . provided hints that Ganymede has a subsurface ocean during . exploration of Jupiter and its moons from 1995 to 2003 . Scientists told reporters on a conference call that it took . some detective work to confirm the discovery . In this artist ’ s concept , the moon Ganymede orbits the giant planet Jupiter . A saline ocean under the moon ’ s icy crust best explains shifting in the auroral belts measured by Hubble . Scientists first suspected an ocean in Ganymede in the 1970s , based on models of the large moon . NASA 's Galileo mission measured Ganymede 's magnetic field in 2002 , providing the first evidence supporting those suspicions . The Galileo spacecraft took brief 'snapshot ' measurements of the magnetic field in 20-minute intervals , but its observations were too brief to distinctly catch the cyclical rocking of the ocean 's secondary magnetic field . Like Earth , Ganymede has a liquid iron core that generates a. magnetic field , though Ganymede 's field is embedded within . Jupiter 's magnetic field . That sets up an interesting dynamic . with telltale visuals - twin bands of glowing aurora around . Ganymede 's northern and southern polar regions . As Jupiter rotates , its magnetic field shifts , causing . Ganymede 's aurora to rock . Scientists measured the motion and . found it fell short . Using computer models , they realized that a. salty , electrically conductive ocean beneath the moon 's surface . was counteracting Jupiter 's magnetic pull . 'Jupiter is like a lighthouse whose magnetic field changes . with the rotation of the lighthouse . It influences the aurora , ' said geophysicist Joachim Saur , with the University of Cologne . in Germany . 'With the ocean , the rocking is significantly . reduced . ' Scientists ran more than 100 computer models to see if . anything else could be having an impact on Ganymede 's aurora . They also repeated the seven-hour , ultraviolet Hubble . observations and analyzed data for both belts of aurora . 'This gives us confidence in the measurement , ' Saur said . NASA Associate Administrator Jim Green called the finding . 'an astounding demonstration . ' 'They developed new approach to look inside a planetary body . with a telescope , ' Green said . Ganymede joins a growing list of moons in the outer solar . system with subsurface water . On Wednesday , scientists reported . that Saturn 's moon Enceladus has hot springs beneath its icy . crust . Other water-rich worlds include Jupiter moons Europa and . Callisto . NASA Hubble Space Telescope images of Ganymede 's auroral belts ( colored blue in this illustration ) are overlaid on a Galileo orbiter image of the moon . The amount of rocking of the moon 's magnetic field suggests that the moon has a subsurface saltwater ocean . Scientists estimate the ocean is 60 miles ( 100 km ) thick , 10. times deeper than Earth 's oceans , and is buried under a 95-mile . ( 150-km ) crust of mostly ice . 'It is one step further toward finding that habitable , . water-rich environment in our solar system , ' said astronomer . Heidi Hammel with the Washington-based Association of . Universities for Research in Astronomy .
Finding resolves a mystery about the largest moon in the solar system . the Space Telescope indicates Jupiter - sized moon has an ocean .