"Concern" ?

It may spread life to other planets and systems, and this would mean that life has higher chance of survival no matter if humans are here or not.

If we look over the next 10 thousand years, we have more chances to have the planet survivability highly affected by a nuclear war, than to have tardigrades secretly building a spaceship and attacking us back in Space Wars style.

It's great if plants and animals spread to other planets, those who can survive will survive, and the others may mutate or adapt.

In the long-term, contamination is going to happen anyway due to humans planning to live there.