Re:RTGs (Score 1)

I agree with 1) and 2) and your point is well taken, but 3) is a bit off. A typical smoke detector contains 0.2 milligrams of Americium 241 and a radioactivity of about 1 microcurie. The RTGs in Cassini use about 33 kg of Plutonium 238 with a radioactivity of 17.4 curie per gram. Cassini therefore has the radioactivity of 2.87 quadrillion smoke detectors.