Define alien. If by alien you mean some intelligence well it's a double edged sword. History teaches us that when two cultures meet usually the superior one wipes the weaker one out. Violence is not a prerequisite.
Alien life is another matter and there you will find a lot of people looking all over the solar system for life a bacteria thank you very much will do just fine.
The problem is, we may not actually know if we encounter any. I think it was Isaac Asimov who said something about aliens not just being different than we imagine, they'll be different than we CAN imagine.
Well when you figure out how to travel millions of light years in a direction of which you can't even know if life exists or not in 1 human lifetime, then you will achieve that goal.