We can only start by looking at Mars etc cause we can't reach much further with our current technology, atleast not fast enough. And chances of the life we'd find in the planets close to us is kinda high, but the chances of those being intelligent is rather small. Though it is possible, but probably not going to be close as advanced as us, but I think its kinda 100% that intelligent species do exist out there that are way advanced then us, thinking otherwise is kinda.... Ignorant in my book. Because we have multiple planets similar to us, and it doesn´t take much for a life to be intelligent really, it might have to develop over hundred of thousand if not millions of years. But it surely has had enough time. And not like we have been so advanced for long, we've bearly had our technology for a few years we could say. Imagine some intelligent species(perhaps more intelligent then humans) that had their tehnology 100 years longer then us, or 10.000 years. Even 10.000 isn't a long time when you know how long planets have been around for.