Earlier quoted context omitted.
Yes. Any one of these things would be a massive boon to our understanding of life throughout the solar system and broader universe, right down even to here on Earth. All three of them would arguably mark a new era in Earth's history.
we are very screwed if they find life on Mars. It means life is incredibly common and thus the Great Filter theory is true and we only have a few years left as a species most likely.
I find it extremely hard to believe you could kill every human being on earth at this point. We’ve reached critical mass, we aren’t going anywhere. When we had that few thousand individuals population bottleneck in the past was when it was dicey. What sort of event could kill every human and end our species? I can only think of planet-wide extinction events like massive asteroid impacts that sterilized the whole earth. And we haven’t ever had one of those in billions of years. Call me too optimistic but I think humans are too resourceful. Some of us would survive anything smaller.