This Cassini spacecraft view of Enceladus shows the moon’s active south pole and its “tiger stripes.” (credit: NASA/JPL/Space Science Institute)

On Wednesday, a school-bus sized spacecraft will dive out of the inky blackness of space more than one billion kilometers from Earth and zip through an icy plume that springs from the south pole of Enceladus.

Although it’s just a tiny satellite of Saturn—less than one-sixth the size of Earth’s moon—Enceladus has become one of the most intriguing bodies in the Solar System. Earlier this year, NASA confirmed that in addition to the moon’s geyser-like plumes, it has a global ocean beneath its icy crust. Where there is water and energy, scientists believe, there’s the possibility of life.

A last flyby

At this point, the venerable Cassini spacecraft, which made these astounding discoveries during the last decade spent exploring the Saturn system, has expended most of its fuel. Before Cassini runs dry, however, NASA scientists say they will take one final, long look at Saturn’s mysterious moon. On Wednesday the spacecraft will dip down to within 50km of Enceladus’ surface—closer than ever before—and fly through one of its plumes.

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