Intriguing Europa

For many years, astronomers have wondered about Europa.  It's surface is scarred by a myriad of cracks, and Cassini has determined the unmistakable signature of liquid water.  Because water is known to be the essential ingredient for "life as we know it (Jim)" the obvious connection is that if we are to find life anywhere else in the solar system than here on Earth, it is more likely to be on bodies where water exists.  Even though temperatures on this icy moon of Jupiter are extremely low, if liquid water can show to exist, then conditions suitable for the formation of some form of life could well exist.

Well, scientists have now found the best evidence yet for water just beneath the surface of Europa.  Analysis of the moon's surface suggests plumes of warmer water well up beneath its icy shell, melting and fracturing the outer layers - hence the scarred and cracked surface which we see.  The results, published in the journal Nature, predict that small lakes exist only 3km below the crust.  Any liquid water could represent a potential habitat for life.  From models of magnetic forces, and images of its surface, scientists have long suspected that a giant ocean, roughly 160km (100 miles) deep, lies somewhere between 10-30km beneath the ice crust.

Many astro-biologists have dreamed of following in the footsteps of Arthur C Clarke's fictional character David Bowman who, in the novel Odyssey Two, discovers aquatic life-forms in the deep Europan sea, but punching holes through the moon's thick, icy outer layers has always seemed untenable.

The discovery of shallow liquid water by an American team makes a space mission to recover water from the moon much more plausible.  The shallow lakes also means that surface waters are probably vigorously mixing with deeper water.  The icy eddies could transfer nutrients between the surface water and the ocean's depths, which could make Europa and its ocean more habitable.  Glaciologists have been studying the surface of Europa for many years, trying to work out what formed its scarred, fractured surface.  By looking at Antarctica, where we see similar features - glaciers and ice shelves - we can infer something about the processes that are happening on Europa.  Upwelling of warmer water causes melting of surface ice, forming cracks. Freezing of water between the cracks occurs so you end up with the existing ice cemented in with new ice.  The underside then freezes again, which causes the uplifting.

The US and Europe are working on missions to Europa, and Jupiter's other moons, which they hope to launch either late this decade or early in the 2020s.

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