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Europa\u2019s subsurface oceans are thought to contain twice as much water as all of Earth\u2019s oceans combined. Measurements of the moon\u2019s magnetic field also hinted that this water might be salty, suggesting it is in contact with a rocky seabed \u2014 a potential source of life-giving energy.\u00a0<\/p>\n
If the liquid ocean really is there, it could make Europa an especially promising place to look for life. But many mysteries remain about this moon, from the thickness of the ice shell to the details of what happens beneath it.\u00a0<\/p>\n
NASA\u2019s Europa Clipper mission, which is due to launch in 2024 and arrive at Jupiter in 2030, would confirm whether Europa does indeed have a subsurface ocean capable of supporting life.<\/p>\n
Europa\u2019s appeal in the search for life is matched, and even exceeded, by Enceladus. The moon of Saturn shares a few key characteristics with Europa, including an icy shell that shows hints of hiding a liquid water ocean beneath it. Like Europa, the subsurface oceans of Enceladus show signs of making contact with a rocky seabed, which could provide energy for life forms in those waters. But where Enceladus outdoes Europa is in the accessibility of its ocean for study.<\/p>\n
Enceladus\u2019 south pole is covered in a series of fissures through which plumes of water have been observed shooting up into space. This makes sampling the moon\u2019s subsurface ocean much easier than it would be to sample water hidden below tens of kilometers of icy crust, which might be the case with Europa.<\/p>\n
In fact, NASA\u2019s Cassini Saturn orbiter flew through Enceladus\u2019 plumes several times between 2008 and 2015, adapting one of its instruments to analyze the composition of the water. Within the plume, Cassini detected a variety of organic molecules including phosphorus, one of the ingredients for amino acids that has never previously been found in extraterrestrial oceans.<\/p>\n<\/div>\n