Europa!

NASA scientists recently announced they are planning a mission to Jupiter's icy moon, Europa, to find out if the distant moon is capable of supporting life.  While the mission is only in the concept stage, and is years away from realization, it shows that NASA is seriously thinking beyond Mars for the potential of life in the solar system.

Jupiter's icy moon, Europa, as seen from the Voyager spacecraft (NASA).

The proposed mission would launch two landers in 2020, and each would be laden with 36 kg of scientific equipment.  Included would be seismometers to measure any seismic activity on the moon, as well as spectrometers to search for organic molecules and the building blocks of life.  It has been speculated that Europa might harbor life, as the moon is covered in a thick crust of ice, and some miles down may in fact have a giant ocean of liquid water.  Just last month scientists discovered there may even be shallow lakes of water right beneath the surface.

Any mission to the Europan surface would have to be a relatively quick one.  Jupiter constantly bombards the moon with massive amounts of radiation.  Without the aid of radiation shielding, a lander couldn't be guaranteed to last more than seven days on the surface of Europa, and mission scientists aren't interested in sacrificing scientific equipment for heavy radiation shielding.  Still, seven days could provide a bounty of information on the mysterious world.

Artist's conception of a lander approaching the Europan surface (futureplanets.blogspot.com)

With a potential price tag of $800 million, this proposed Europa mission would likely cost more than NASA's recent, inexpensive, New Frontiers missions, which usually run around $400 million.  However, it would likely be less expensive than a so-called 'flagship' mission, which can run into the many billions of dollars.  There had been some talk of a potential flagship Europa orbiter mission, in which NASA would have teamed up with the European Space Agency for two Jupiter system orbiters.  However, recent budget constraints have most likely killed the American portion of that mission (the ESA may continue the project without NASA support).

A mission to explore the habitability of the far flung moons of our solar system is inevitable.  Europa and Ganymede both contain large amounts of water, and Jupiter's gravitational pull may create enough friction to keep some of that water in a liquid state.  Saturn's moon Titan, which was visited by the Huygens probe back in 2005 as part of the Cassini mission, is also a prime candidate for life.  Titan is covered in lakes of hydrocarbons, and indeed has an entire climate system based on liquid methane and ethane in which life forms might flourish.  I do hope that NASA makes visiting these worlds a priority, as unlocking their secrets will undoubtedly lead to a greater understanding of how our solar system formed, and possibly reveal whether or not life ever evolved on a planet other than our own.