The great filter is based on the idea that established intelligent life would be easy to spot and so must not be common. That’s quite the assumption. If we discovered that there has been intelligent life a mere 0.000008 light-years away this whole time, I would think it strong evidence of the opposite, that it is probably common but hard to notice even next door.
Meanwhile, though, is anyone else a little annoyed of constantly trying to make all exploration about life? Yes, methane is a sign of life on Earth, with its reactive oxygen-rich atmosphere and evident carbon-based ecosystems. That doesn’t mean you wouldn’t expect it without life on planets without such conditions. We should be able to be interested in Mars for reasons other than invented biology, thank you. If nothing else you’d think prospecting could sell missions.
