Should you go to Mars? ft Bill Nye

Here's to TPS.
Question thrown out there to toy with about bringing our own microbes and us then not being able to tell them apart from Martian ones: if there is indeed microbial life on Mars it'd be subsurface. The surface itself is sterilized by constant harsh radiation; Mars' electromagnetic field has been diminished. The same would happen to any surface of suits and equipment, and the only Earth microbes that would survive would be inside us, and inside the suits, hermetically separated from the outside. Thus contamination could only occur in the lab. 
But Mars life, if it exists, has been evolving far, far away from Earth. Even here on Earth it is possible to determine geographic origin in microorganisms. One should think that someone with sufficient qualification would be able to distinguish. This would still be the case if panspermia had occured, i.e. microbes being flung into space with debris that reached enough velocity to leave Mars after an asteroid impact and subsequently coming down here on Earth, making us all Martians. The time involved since would still make microbes alive on Mars today noticeably different.
While we must still be as cautious as possible, the possibility of contamination is manageable.