Anyways Uranus , neptune are distant planets from Sun so we may not expect the sort of life-form we are looking for.And you don't see any life there becuase , you haven't been there and completely searched the planet. Have you , haha ??
we are a carbon based life form, that means, carbon forms the most important part of our bodies.
now imagine a creature formed of chlorine, silicon, methane. oxygen would be deadly to it. water would just dissolve its structure (like acids do to us). it would prolly look like a cross between a tortoise and a rock. how would you know its "life"?
Interstellar travel takes a lot of time, but you know, there could be ways to overcome that problem. long living species comes to my mind... cryogenic freezing, bending the laws of physics.. etc.
Humans haven't explored Uranus or Neptune completely till now.So you can't say they don't have any sort of life form(in past/future/present) , there is always a possibility.
And If there was water on MARS(in liquid state) ,balanced atmosphere was sort of necessary to hold it in that state.
Also water is a necessity for sustaining life form similiar to our own.With adequate amount of pH value, mineral content , etc.
what balance? you can have water in a world with atmosphere made of noble gases, nitrates, cyanides, etc, its not gonna affect the "balance" in any way.
Btw , who said that water alone is sufficient for known-life-form to exist , atleast I Didn't ??? SOil , Climate, temperature , atmosphere, and a lot other factors play a major role.
I was talking specifically about MARS , since it has many other similiar features alongwith traces of WATER. Maybe you should think think deeply on that.
you were the one who was making dubious assumptions about conditions on mars. nope, neither soil, nor climate are anyway related to finding life. you can find life in arid tundras and hot deserts............
BTW , I read in above posts that you don't like to read about fables of dead planets(or history ) , so please stay away from my comments , since they might talk about fables itself and might hurt your sentiments .
And hating history isn't such a good idea Sir.
hate history??
Maybe someday they will across fossils. : p haha
However the question that scratches my brain a lot is that { if there was life on mars , something very sudden and tragic might have happened to force complete extinction }If the change was slow, species should have evolved themselves.