How likely is it that we have already accidentally "contaminated" other planets or moons, despite procedures to prevent this?
It seems unlikely to be possible to completely prevent all lifeforms from hitching a ride
replies(2):
It seems unlikely to be possible to completely prevent all lifeforms from hitching a ride
https://www.liebertpub.com/doi/10.1089/ast.2011.0738
I worked with these organisms from the space station. Their resistance to things like hydrogen peroxide (what we wash space probes with) is incredible.