I see here most people saying it is, & i hate to say that who I'm saying it's not, cause I'm 19 years old, since last year whole my life i was a prefect believer of aliens & some where from inside i was contacting it I loved all books & movies about it, but truth is , it's not real, it's Just for making people believe to somewhere beyond earth is some strange peoples & they're ready to attack us, & we need to protect ourselves & be ready against them, in fact those special people are exist, "Earth" this planet that we're living on , is only a little spot between thousand planets around us, so those peoples are exist but it's not Aliens , & i can say more but i don't want trouble ;) you don't know me so i don't think you could believe my words but trust me they're not real they're Just made up to play with our mind, I saw things as proof but sorry i can't tell it, so in the end your choice, Good Luck :)
the universe is so big that it is possible. when the universe formed. earth was formed with conditions suitable for life. why not other planets hundreds of light years out there. on the discovery channel, scientists had discovered a planet that was all water. the water was estimated to be 10 miles deep. who knows what might be in there. one of Saturn's moons is all ocean but is frozen at the top. it could have life in it.