NASA's Cassini spacecraft has measured a curious abundance of methane spewing into the atmosphere of Saturn's icy moon Enceladus. A team of American and French scientists published findings in Geophysical Research Letters suggesting two scenarios that could explain the methane abundance observed in the plumes.
In 2005 Cassini's magnetometer and imaging data revealed the surprising existence of geysers in the south polar region ejecting water vapor into space. Scientists now believe that Enceladus harbors an internal liquid-water ocean under tons of icy crust, and that the plumes originate there. Analyzing the composition of the plumes, therefore, can provide a direct window to what is happening in the inner ocean. Cassini has since flown through the plumes, allowing scientists to determine that these watery geysers contain other volatile species, including hydrogen, carbon dioxide, ammonia, and methane. Volatiles are chemical elements and compounds with low boiling points that are associated with a planet's or moon's crust or atmosphere.