Re: Definition of alien life
You are correct in asserting that just because it's very salty doesn't mean there isn't life but at the same time from what we know of life it seems to make it less likely. Earth is a surprisingly hospitable place for life and yet after 3.6 billion years very little has managed to adapt itself to live in very salty water. You could argue that the reason for this is that all life on earth, at the cellular level, uses (very) broadly the same building blocks and perhaps those blocks can't be adapted for highly salty environments. The problem then is why hasn't weird and wonderful types of salty-environment-loving life appeared on earth?
When we get out into the stars (or even perhaps just the solar system) my guess is that we will occasionally find life on moons / planets that aren't even close to habitable for earth life but they will be few and far between compared to life on earth like planets. Shame we won't live to find out if that's correct.