Interesting topic for sure!

Answering this question everybody has to know if we talk about live an mars we are talking about some bacteria or microbes and not about aliens and that sort of stuff.
We know water bear (Tardigrada) is able to sustain the levels on mars so basically it could live on mars (if there were some kind of food source, but there isn't). It is always difficult to answer this question with certainty but for me, as a biology and agriculture student, water means live and since we all know mars once had water on it I'm quite sure there had to be some live up there at some point.

On the other side there is still much to discover at our planet, like the deep sea. I'm convinced there are more alien looking specimens down there than in our solar system.