As most of you will recall, there was considerable public outcry when the Cassini probe was launched with its nuclear power supply. However, no alternatives to nuclear decay were offered as a power source. The main thinking seemed to be that the probe should just go without the power it provides. This got me to wondering about a power source which seems rather obvious to me. I know that when we send a probe to Jupiter, we have to shield it pretty heavily against the fierce radiation around that planet (not sure if the same is true for Saturn). It seems to me that shielding a probe against radiation, and then supplying it with an internal source of radiation to power its electrical systems is ironic, to say the least. Doesn't it seem like there ought to be some way to use the copious amounts of raditation coming from the planet for a power source?