Do Aliens Exist?

I believe that there could be life on other planets. I think that because since scientists found frozen water on the planet "Mars" that  aliens could have drank from that water. Even though no signs of life was found on upperground there could be life underground. If life did exist on other planets I think they would resemble small underground mammals. They would have mouths to drink, and eat. Noses for sniffing and breathing. And feet for walking. Some species might have hands and arms like a human. These are all the reasons of how organisms would look like on other planets if life did exist there.