Originally Answered: Did they somehow sterilize rovers to prevent contamination in Mars?
The original aim of Carl Sagan etc when they devised the early planetary protection requirements was to make it less than 1 in 1000 chance of contaminating Mars in the exploratory phase. And I think that is still the basic philosophy for Mars though the ideas about actual requirements have changed.
Though there have been several lapses e.g. spacecraft crash on Mars that weren't sterilized for the surface - on the other hand the surface has turned out to be more hostile to life than originally expected. Especially where Curiosity landed, it is very dry, and no ice on the surface or near the surface, but you do still have morning frosts because you get 100% humidity at night. It's not impossible that there might be life there, there are ways it could survive (the advancing sand dunes bioreactor model) and some think that Viking detected life in a broadly similar location on Mars. But without ice, it's pretty hard.
So anyway - general consensus is that it is unlikely that we have contaminated Mars yet, though nobody can be sure by nature of statistics and probability.
For more about this, see Planetary protection (wikipedia). I helped write that myself, it's reasonably accurate.
If we did find that the 1 in 1000 chance has happened and that Mars is contaminated by some Earth microbe, still - we should take even more care not to contaminate it with anything else. It's like protecting the wildlife in Australia. or some island. If you find you have accidentally introduced rabbits, then you take even more care to make sure you don't introduce feral cats and dogs, rats, and cane toads.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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