I did 'a bit' of searching and found the below info. There should be one or more detailed papers/pdf's in the web (I'm pressed for time right now *g*) Regarding the Galileo probe and sterilization:

[4. Jupiter: Assuming any terrestrial organisms survive the destruction of Galileo during entry into Jupiter's atmosphere, the only environment in which they can conceivably survive is in the atmosphere itself. But any free-floating organism that finds itself in a benign region of the atmosphere will be rapidly convected into a less favorable region and, thus, the chances of survival are essentially nil.13 In addition, the committee notes that no special planetary-protection procedures (e.g., bioload reduction or sterilization) were applied to the Galileo Probe, which was specifically designed to survive penetration to the 10-bar level in Jupiter's atmosphere. Therefore, COMPLEX sees no objection based on planetary-protection considerations for the disposal of Galileo by impact with Jupiter.

Thus, COMPLEX concludes that collision with either Io or Jupiter is the most appropriate planetary-protection strategy for the disposal of Galileo. Based on Dr. Johnson's presentation, the committee understands that operational considerations point to Jupiter as NASA's preferred option. COMPLEX concurs with this decision.]

From:
http://www.nationalacademies.org/ssb/galileoreport.htm

Some info on Stardust:
http://stardust.jpl.nasa.gov/tech/aerogel.html

Amazing little invention, that Aerogel! I'm nit-picking when I think that they should have given Stardust another panel of aerogel to work with... one or two that would extend at the right time to collect particles from different parts of the journey (asteroid belt neighborhood, etc.), as opposed to 'clumping' all particles together on one side of the gel sheet. I know they've chosen one side that will concentrate/pick up the particles of Comet Wild 2.

Too much fun. :)

Cheers,

Marcia