Enceladus' Cometary Plumes

[davesmith_au]

08/03/12 ~ Wallace Thornhill

Today the Cassini spacecraft is due to swoop over the south pole of Enceladus, one of the inner moons of Saturn, at a height of 50 km (30 miles), sampling its celebrated south polar plumes. The analyzers will "sniff and taste" the plume. Information on the density, size, composition and speed of the gas and the particles will be collected. 


[...]

According to the usual geological arguments, Enceladus’ plumes require some form of internal heating. Of course, NASA is quick to exploit any suggestion of subsurface liquid water on another body in the solar system as a reason for further missions to look for signs of life. But a source for that heat is not apparent. Susan Kieffer, a geology professor and planetary scientist at the University of Illinois at Urbana-Champaign, observed, "This tiny satellite should be cold and inactive, like our own moon. But it isn't." Modeling the maximum heat available from tidal distortion and radiogenic heating from a rocky core fails by an order of magnitude to explain the energy of the plumes. It also fails to explain the concentration of heat at Enceladus’ south pole. So, what if Kieffer’s intuition was correct and Enceladus is “cold and inactive?” Could the measured heat and the energy to drive the plumes come from space? ... [more...]