OK - I'm not really sure what truth science clings to without evidence, but I'll share my thoughts on Martian life!
I think any current Martians (like microbial life) would live just under (or at least not too deeply) under the surface of the planet. That would keep them safe from the most powerful UV rays and also help insulate them from the extreme temperature changes - unless they traveled along the terminator or grey line. The latter seems unlikely.
Under the surface would also be where any microbes, germs, etc.. would possibly find liquid water. Or at least maybe some kind of muddy slush. Though there is some evidence that the polar caps do occasionally melt slightly though this hasn't been directly observed.
Personally, I am more intrigued with the possibility of life on some of the gas giant moons. Titan may be very similar to the Earth when life first got its foothold and Europa is a water world(albeit frozen). Depending on how life begins and evolves on other planets, these moons seem the most likely candidates in our solar system for extra-terrestrial life. Especially considering the new life forms we are discovering at the ocean's greatest depths (hot vents and cold seeps). These conditions are the closest environment we have to space in that they are the most severe. Although Antarctica is no picnic either - a frozen desert with little precipitation with temperatures that can reach -129 F (-80 C)!! And life is there so it isn't too farfetched to think life can survive on Mars where temperatures are more servere with lows in the -220 F (-140 C) range.
But even the gas giants, especially Jupiter, may contain some kind of life - though without a solid surface the life form would have to "float" or "fly" through the atmosphere from birth to death.
It does seem inconceivable that humanity is the only life in the universe and I would be surprised if it were the only life in this spiral arm of our galaxy!
Intelligent life, on the other hand, may not be as likely but when dealing with astronomical numbers (literally) the chances of the "impossible" happening are greatly increased. I mean - we're here, right?