Earth Bacteria Surviving on Mars

As spacecrafts cannot be sterilized completely, is there a possibility that we have accidentally contaminated mars with life during space missions. Researchers have even discovered new strains of evolved bacteria that were carried unintentionally to the international space and survived there for years. I think it's very likely that we have sent earth bacteria to mars and wherever else we have sent spacecraft. Like you said, certain bacteria are very hardy. They don't die. They can survive in the vacuum of vacuum of space.