Not impossible, but the higher solar energy and denser atmosphere available on Earth make it more likely that life started first and evolved faster here than on Mars. But exchange of early life forms cast in space between the two planets isn't impossible, it could have happened, due to meteorites fallen in the seas, for example.

life on other planets do exist. i believe in that more than life not existing on other planets. Think of how big the universe is! we can't possible be the only planet with life on it!

if we ever will get in contact with other lifeforms depends on how far we can travel. i mean we might never find anything on mars or any other planets in our soler system or even in our galaxy. but maybe they will find us hopefully though not to invade our planet though it would be cool as well as humans would unite for once lol (stupid humans killing each other).

but what if they already have found us and have been here for many years. it is a possibility i mean who could prove it wrong or right?

I don't believe in extraterrestrials or life forms outside the earth's atmosphere.

However, I do believe in extraordinary terrestrials.

I don't remember where I read this, but here are the stages of intelligence: 

- Reflex (ex. plant)
- instinct (ants, spiders, flies)
- memory (most animals)
- reason (Humans, some mammals)
- feelings (Humans, some mammals?)
- will (only humans)

I would assume an intelligent creature would be somewhere between instinct and memory.  

Care to elaborate?

nah, because it will turn into a religious debate, and I prefer to keep my religious beliefs to myself.

But I will correct myself. I believe in God and angels, so my prior statement was completely wrong. However I don't believe in extraterrestrials as the OP depicts them.

no fun : (

So you think we are the only intelligent life forms in the whole Universe?!?!

That's tough to answer without sounding like a religious nut-job

Fixed for you.