Is there any evidence that leads us to speculate that there are, or may have been, microscopic life on Mars?

Question

Anything?

Answer 1

The only real evidence was a possible segmented microscopic portion of a meteorite that fell to Earth that was kicked off Mars during an asterdoid strike;  It's inconclusive if it's a natural rock formation, or the result of fossilization.  On the surface, the robots we have up there haven't been able to prove life exists or once existed.  

Answer 2

Nope, the meteorite that they found in Antarctica that started so much hype about being fossilized microbial life was actually naturally forming geology... not fossils.

So far the only thing we have on life on Mars is that there is frozen water and geology suggest it may have flowed on Mars's surface at one time... no solid evidence though.