Matt_dk writes: Scientists working on the Cassini space mission have found negatively charged water ions in the ice plume of Enceladus. Their findings, based on analysis from data taken in plume fly-throughs in 2008 and reported in the journal Icarus, provide evidence for the presence of liquid water, which suggests the ingredients for life inside the icy moon. The Cassini plasma spectrometer, used to gather this data, also found other species of negatively charged ions including hydrocarbons. Link to Original Source
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"