First they’d have to closely examine if it wasn’t cross contamination. We’d have to make sure it wasn’t something we brought along with us or with our rover or space craft from Earth.
It would be a very big deal. It’s the holy grail in the age-old war between religion and science!
It would mean life could exist on other planets and therefore life could evolve on other planets, somewhere, and it would mean there might be intelligent life out there somewhere.