Afaik it is very unlikely anything from mars can affect us in any way. All our bacteria and viruses have millions of years of coevolution.

Best example is how almost all cat and dog infections do not affect humans. And cats and dogs are mammals!

Sure, but you missed my entire point, which was we don't want to contaminate the samples.

The entire point is looking for evidence of life and organic material. Would be a shame to spend all those billions just to not be sure if the organic material we're looking at came from Earth or Mars.