Aurora shift confirms Ganymede’s ocean | Science News

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Aurora shift confirms Ganymede’s ocean

Jupiter moon’s underground saltwater explains Hubble telescope observations

By
4:18pm, March 12, 2015
Ganymede

SEA SIGNS  Shifts in Ganymede’s version of the Northern Lights, illustrated here, suggest that a saltwater ocean lurks beneath the icy crust of Jupiter’s largest moon.

Jupiter’s largest moon, Ganymede, has solidified its membership in the growing cadre of solar system locales where liquid water flows beneath the surface.

“The solar system is now looking like a pretty soggy place,” Jim Green, director of NASA’s Planetary Science Division, said March 12 at a news conference.

The ocean showed itself not with plumes or pools but via subtle changes in Ganymede’s aurora, the moon’s version of the Northern Lights. Jupiter’s magnetic field should interfere with Ganymede’s, causing the moon’s aurora to rock back and forth by about 6 degrees. Observations with the Hubble Space Telescope, however, showed that the aurora shifted by only about 2 degrees. Joachim Saur, a geophysicist

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