Is the idea really that the moons of Saturn might be contaminated by microbial life that has survived attached to Cassini for 20 years? But we're not worrying about the Mars landers? I don't get it.
Saturn's moons are much more likely to spread any contamination due to the presence of liquids. Liquid water on Enceldus and hydrocarbon lakes on Titan.
I assume you're just guessing, right? We already landed something on Titan! And small patches of liquid brine exists on Mars; obviously unlikely, but so is Cassini drilling through 5 miles of ice to reach to liquid water water inside Enceladus.
