The Habitability of Enceladus from Cassini and Enceladus Life Finder as the Next Step

Enceladus is a tiny moon circling Saturn. Through Cassini's discoveries we now know that it has a global, geologically long-lived salt-water ocean inside, in contact with the silicate core, at which interface there is moderate-temperature hydrothermal activity perhaps akin to the Lost City vent structure on Earth's seafloor, which hosts a rich ecology. The ocean water, containing nanosilica grains from the hydrothermal vents, and large organic molecules not yet identified, is expressed directly and continuously into space via fissures in Enceladus' south polar region. Cassini has analyzed the composition of ice grains and gas by repeatedly flying through this plume on multiple flybys, so now we know how to detect unmistakable signs of ocean life with modern instruments on a subsequent mission. This makes Enceladus a natural laboratory for understanding how life - carbon- and water-based but not sharing Earth life's origin -arose. To do so quickly without waiting for the next Flagship opportunity requires a focussed mission that applies the most focussed and robust analytic techniques on the most easily accessed samples of the ocean—the plume itself. Enceladus Life Finder (ELF) was proposed to do just this, and we describe why a graceful, elvish approach to life detection is optimal.