A recent letter (Voice, Oct. 5) regarding the peril due to the plutonium carried aboard the Cassini space mission seriously overstates the potential hazard of the actual material involved.
Like many other elements, plutonium has several isotopes, all of which are radioactive. However, the isotope involved in the Cassini probe is plutonium 238 which has an 80-year half-life, emits beta particles and is not readily fissionable. This is in contrast to the more commonly known isotope, plutonium 239, which has a 25,000-year half-life, emits alpha particles and is highly fissionable; hence its use in nuclear weapons and as a nuclear reactor fuel.
Plutonium 238 has been used successfully and safely as a power source in a number of U.S. and Russian space vehicles over the past several decades.
