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 flight through open space and fiery entrance through the Earth’s atmosphere...
I mean, c'mon, like, that's GOTTA be from, like, Venus or Andromeda or some s*** like that. Eyeballs don't grow on trees!