Is There Life Within Europa's Ocean?
Europa appears as one of the most enigmatic of the Galilean satellites. With a mean density of about 3.0 g cm-3, the Jovian satellite should be dominated by rocks and water. Ground-based spectroscopy, combined with gravity data, suggests that the satellite has an icy crust kilometers thick and a rocky interior. The Voyager images showed very few impact craters on Europa's surface, indicating recent, and probably continuing, resurfacing by cryovolcanic processes.
If liquid water is present within Europa, it is quite possible that it includes organic matter derived from thermal vents. Thus, the possibility of a terrestrial-type life present in the hypothetical ocean of Europa must be seriously considered. The most likely sites for extant life would be at hydrothermal vents below the most recently resurfaced area. On the other hand, biological processes in and around hydrothermal vents could produce biomarkers that would be erupted as traces in cryovolcanic eruptions and thereby be available at the surface for in situ analysis or sample return. Mineral nutrients delivered through cryovolcanic eruption would make the same locations the best candidates for photosynthetic life.
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