Credit: NASA/JPL/Space Science Institute
Few people had probably even heard of it before Cassini arrived, but small, icy Enceladus is now easily one of the most interesting and mysterious worlds in the Solar System. Two new articles on Enceladus now grace the Cassini homepage, and I heartily recommend reading them both. The first concerns the question of why exactly this little moon's south pole is shooting jets of ice and water vapour into space. A subsurface body of relatively warm liquid water seems like quite a good suspect so far, but I wouldn't discount other contending hypotheses just yet.
The second article explains how tiny Enceladus, just 500km across, has an effect on the whole Saturnian system. The ice it ejects weighs down Saturn's magnetic field by creating a "plasma donut" that is then absorbed by the A ring.
"This is an example of how Saturn's rings mitigate the overall radiation environment around the planet, sponging up low- and high-energy particles," says [William] Farrell [of NASA's Goddard Space Flight Center]. By contrast, Jupiter has no dense rings to soak up high-energy particles, so that planet's extremely high radiation environment persists.
Cassini will be flying past Enceladus at a minimum altitude of 50km - an astronomical hairbreadth - sometime in March.