Fresh organics found in Enceladus plumes hint at habitable ocean

Scientists analyzing data from NASA’s Cassini spacecraft say they have identified fresh complex organic molecules being ejected from the south polar plumes of Saturn’s moon Enceladus, a finding that strengthens the case that the moon’s subsurface ocean may be capable of supporting life. The observations derive from a close, high-speed flyby of Enceladus in 2008 during which Cassini sampled ice grains emerging from the moon’s geysers.

The measurements were made with Cassini’s Cosmic Dust Analyzer as the spacecraft passed through the plume at roughly 11 miles per second, or about 18 kilometers per second. That high impact speed reduced signal interference from clustered water molecules and allowed scientists to detect molecular signatures that had been masked in earlier, slower-sampled material. The analysis found many of the same organics that had been detected previously in older particles that populate Saturn’s E ring, and it also identified additional organic compounds not previously seen in the plume samples.

Researchers say the presence of these molecules in freshly ejected grains indicates they originate in Enceladus’s subsurface ocean rather than being products of...