SPACE EXPLORATION
How did we find an ocean on Enceladus?
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The first confirmation that there was a liquid layer about 35 kilometres (21.75 miles) below the south-polar terrain came from the gravity signature. The distribution of mass under the south-polar terrain was detectable by carefully tracking the motion of the Cassini spacecraft as it flew closely over Enceladus’ south pole. Doing three such flybys allowed the gravity team to figure out that the water layer had to be about 35 kilometres (21.75 miles) beneath the surface and about ten kilometres (6.21 miles) thick.