article_snippet.sent: Scientists using the Hubble recently provided powerful evidence that Jupiter's moon Ganymede (pictured) has a saltwater, sub-surface ocean, likely sandwiched between two layers of ice .
article_snippet.sent: The space agency is also planning a mission to Europa, which may launch as early as 2022.
article_snippet.sent: The space agency hopes to find out whether the icy moon is habitable.
article_snippet.sent: New Horizons took this image of the icy moon
article_snippet.sent: Europa rising above Jupiter's cloud tops. 
article_snippet.sent: The space agency is planning a mission to Europa, which may launch as early as 2022, to find out whether the icy moon is habitable .