What earth shattering evidence has Curiosity found on Mars?

How do we know that any biologic samples are not the result of contamination from the probes that we sent to Mars over the last decades? After all, scientists believe the much more implausible theory that life came to Earth aboard chunks of Martian soil blasted from the surface of Mars by a meteor impact, survived a frozen flight through open space and fiery entrance through the Earth’s atmosphere... Terry RC, are you out there? What do you think that East Anglia University and its robot consensus of 100,000 scientists have to say about my theory?