Europa's ocean may be closer than we thought

Jupiter's moon Europa is one of only a handful of solar system bodies thought to have a subsurface ocean (Titan, Enceladus, and Triton are others).  Such an ocean would be an ideal habitat for the formation of life.  After all, life on Earth first proliferated in the seas.  In fact, many consider Europa the likeliest place for us to find life in the solar system today (sorry, Mars).  So why haven't we sent a mission to the moon in search of our neighbors?  It's because Europa's oceans are locked deep below the surface - anywhere between five and twenty kilometers down.  The ice sheet covering the water is far thicker than on Antarctica, and probably even thicker than Mount Everest is tall.  We're still struggling to complete tasks in Antarctica, so a Europa drill seems pretty far off.

Europa's scarred surface could make it difficult to find the source of ocean-carried material on the surface.  (Image credit: NASA)

The situation might not be as hopeless at it seems, though.  Recent observations of the moon from here on Earth have found the presence of something called epsomite on the surface.  Epsomite is a magnesium sulfate salt, a kind of mineral which can only form in water.  Since there has probably never been water on the surface of Europa, it must be coming from the oceans below.  This is exciting because it means that there must be a link between the surface and the subsurface ocean.  While we might be a long way from drilling through to the water below, it would be far easier to sample the surface in the area of these cracks.  If microbial life exists in the ocean, its remnants might be present along with the epsomite.  Of course, we still need to find where these cracks are - Europa has a complex surface which could easily conceal the source of these deposits.

So will this expedite a Europa mission?  Maybe, but it's likely that the first mission won't be a lander.  The problem is that we don't have a very good idea about the topography of the surface on small scales.  In order to find a safe place to land, we need to know the terrain to a scale of a few meters or less.  Currently, our maps are only good to a few tens of meters at best.  An orbiter will likely be needed to use a laser to map the surface to much higher detail - on the Earth's moon, our maps are good to less than a meter.  With such data in hand, we could start to plan our the most suitable landing locations for a second mission.

Of more immediate concern, however, is NASA's sequestered budget and its lack of radioactive material to power future space missions.  Before these are taken care of, any trip to Europa will continue to be a pipe dream.

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