Where are the Tharks?

I see where NASA is reporting that mars could have, many billions of years ago, supported life. I will not say "balderdash!" But I will say there's quite a number of assumptions involved to assert that.

At one time, science fiction loved to use Mars as a living planet full of green men (and sometimes red, black, and yellow and even white... see Edgar Rice Burroughs's Mars series). Science ruined that. It revealed the truth about the planet; thin atmosphere, inhospitable conditions, barren of vegetation and life. No canals, no crumbling ancient cities, no sand worms, no life.

NASA says... "wait!... maybe there were once microbes and that would mean life existed." Except they cannot definitively prove life did once exist there. It is wanton speculation, nothing more.

Let me show you an excerpt from a New York Times article:

Several billion years ago, Mars may well have been a pleasant place for tiny microbes to live, with plenty of water as well as minerals that could have served as food, NASA scientists said Tuesday at a news conference on the latest findings from their Mars rover. But they have yet to find signs that actual microbes did live in that oasis.
Mars could have supported life

It goes on to lay out the reasoning... But it is not convincing. Not to me. And I really want to believe. Ok, possibly there were microbes on Mars a mere 3 or so billion years ago. But then the ecosystem changed. All of a sudden, it seems, the planet could not hang onto most of its atmosphere. It's a light-weight... mass-wise... and that meant not enough gravity to to retain the atmosphere needed to sustain life.  And the core cooled and volcanoes stopped erupting. The life-supporting water froze or evaporated and Mars became the cold, dry, planet we know it to be today. Must have been those SUVs those microbes liked so much.

The theory is all based on rocks. Or, actually, on the make up of the rocks. Which suggest an abundance of water and that this water contained nutrients that microbes could use for sustenance.

I don't know... I want giant sand worms and willowy red and purple plants and 6 legged lumbering behemoths ridden by extremely tall green men with tusks.

Microbes just don't excite me. Especially "possible" or "maybe" ones.