Slate has a neat article about NASA's Planetary Protection Officer and what he does. We grouse a lot about the heavy requirements on our Mars landers for thermal bakeout, but it is all for a very good reason: we simple don't want to contaminate Mars with any of our Earthly microbes.
In addition to setting standards for extraplanetary cleanliness, John D. Rummel is also working on Earthly containment:
Rummel's other big challenge is designing and building a suitable containment facility for the analysis of Martian samples. Sometime next decade, NASA hopes to complete a mission that can return up to a kilogram of Martian rock to the Earth. Though there's only a tiny chance that such a sample will contain an organism, let alone one that might cause a nightmarish scenario out of The Andromeda Strain, NASA doesn't want to take any chances with the future of the human race.