As it should, though? At that point in time it was more of "we'll know it when we'll see it".

With that kind of wiggle room, it usually ends up being "We'll disagree when it becomes relevant".

I think parent is refering to wildly crazy nonexistent environment standards back then, like doing surface tests of nuclear weapons.

Remove the word ‘environmental’ and your statement gets better.

That's true, but it's defined (and kept up to date) in practice by COSPAR, who have a pretty elaborate set of definitions in place for Mars in particular.

The rules for Mars aren't based in the treaty but instead on "planetary protection" an abstract policy coming from no law other than forms of regressive environmentalism that tries to limit contamination so that it's easier to find potential microbes. It's already actively harming site selection for Mars exploration by preventing sending of rovers that might discover life to actual areas that might have life.

To save the possibility of finding life we are preventing ourselves from finding life.

COSPAR is (officially speaking) a private body, and as such their Planetary Protection Policy is not legally binding. They propose their policy as an interpretation of Article IX of the Outer Space Treaty, but as a private body they lack the legal authority to make binding interpretations of an international treaty. The standard approach in international law would be to look at the intentions and understanding of the States Parties at the time the Treaty was originally concluded in order to interpret it - which would likely support a far weaker understanding of “harmful contamination” than what COSPAR proposes.