I have also reinstated this statement which they removed from the first para: "The need for planetary protection measures is strongest for missions designed to return a sample from another planet or celestial body to the Earth (back-contamination)." again without discussion.

 The sentence was not written by me. It could perhaps do with a cn, what source actually says this, and if the reader wants to follow it up further, what did they say exactly? Personally I think forward contamination is also pretty important. But certainly not removed without discussion like this.

 The rest is merged material from other articles and as I don't think they belong here I don't want to get involved in editing those sections. The history section was originally much shorter and immediately after the intro, and I don't see the point in the Resilience of life in space section, wouldn't put that as the first, or indeed any section in an article on Planetary Protection. I would just revert the entire thing back to the way it was before WP and BI edited it if it was up to me.