I was under the impression that they have been taking precautions with the various Mars rovers to keep from contaminating Mars with Earth microbes. My understanding is that they are cleaned very carefully to make sure they are sterile. However, having said that there may be some question as to just how sterile they are. Frankly getting something completely sterile while it is any place on Earth is a big job. I expect that anything baked at over 1,000 degrees F (537 degrees C) (my top of the head estimate) would probably be sterile. However, baking an interplanetary probe is kind of problematical and then after baking it you would have to keep it in a totally sealed environment. That all leads to problems with actually sterilizing the probe. So the best we can do is to be as careful as we can be, then if we find signs of life do a very careful analysis to be sure it wasn't a hitchhiker on the probe.
Bill Gill
