[X] My Assistant

[vexgizmo]

OK, it's time to have it out. Is Enceladus really spewing water, or are its fractures effectively sublimating warm ice like a comet?

Have a careful read of the Enceladus Science papers (specifically Porco et al vs. Spencer et al.) and you will see that the evidence for water is equivocal, and arguably circular. The prime piece of evidence for liquid water (Porco et al) is the inferred high ice/vapor ratio of the plume (top of p. 1398). This is inferred from scattering models and assumptions of plume particle sizes and argued unlikelihood of particle entrainment in sublimating gas (explained briefly in their note 30, and into p. 1399). Should we hang our conclusions, exploration strategies, and hopes for life on moels of ice/vapor ratio, particle size assumptions, and inferred difficulty of entraining particles in sublimated gas?

Instead (Spencer et al), the fractures of Enceladus may simply expose warm (T ~ 180K) ice which sublimates like a comet (p. 1405).

Show me the water.

[Guest_BruceMoomaw_*]

All I've got on that is so far is what he says in his EGU and AGU abstracts: "We will present results from laboratory studies on the radiation effects on ammonia–water mixtures pertaining to the environment of Saturn’s icy moon Enceladus. We show that ion irradiation destroys ammonia efficiently, and produces N2 that could be the source of N+ that has been detected in the exosphere. Warming the irradiated mixtures we observe outbursts of water and ice grains at temperatures much lower than those needed for sublimation of water ice. These radiation processes may explain the plume of water vapor and grains observed by Cassini at Enceladus."

...and a barebones PowerPoint presentation of his to the Cassini Plasma Spectrometer team which I've just discovered: http://caps.space.swri.edu/caps/TeamMeetin...OnEnceladus.pdf