Marine Science Goes to Space

When the Cassini spacecraft first flew above the south pole of Enceladus, a moon of Saturn, it did something no solar system explorer had done before: It took a shower. The craft zipped through plumes of water vapor and ice grains spewing from cracks in the icy moon’s surface. Cassini didn’t need to towel itself dry because the spray was thin. Combined with the craft’s earlier images, however, it provided strong evidence that a global ocean lies beneath the moon’s crust. Later analysis found hydrogen, carbon dioxide, methane, and tiny particles of rock in the plumes, suggesting the ocean could contain all the major ingredients for life.

The Cassini discoveries added Enceladus to a growing list of possible ocean worlds in our own solar system—bodies with large amounts of liquid water hidden from view. Some of them could contain more water than all of Earth’s oceans…