Astronomers have spent more than a decade trying to identify the dark substance erupting from geological features on the surface of Europa. Now, a team of researchers at NASA's Jet Propulsion Lab believe they've identified the mystery material as sea salt. You know, from the ocean that NASA suspects is hiding under Europa's icy surface. The team, led by planetary scientist Kevin Hand, began its investigation by building a testing device that recreates the extreme conditions found on the gas giant's moon. "We call it our 'Europa in a can,'" Hand said in a statement. "The spectra of these materials can then be compared to those collected by spacecraft and telescopes."