Erwin Schrodinger proposed a physics experiment. He put a cat in a sealed box. There is also a poison bottle in it also. Before he opened the box, he proposed the cat was alive and dead at the same time.

"Whenever guests came over to his house, he would say: look at the moon. Does it suddenly spring into existence when a mouse looks at it? Einstein believed the answer was no. But in some sense, the answer might be yes." Parallel Worlds, pg158, Michio Kaku.

Keeping this in mind, next time when you are not looking at the moon, the moon might not exist at all...

According to a New York Times articles Hunting for Life in Specks of Cosmic Dust There are some requirements for life on a planet:

• the home star has to be far enough from the galactic centerto be away from lethal black hole pyrotechnics, for example, but not so far into the galactic sticks that stellar evolution has not yet produced enough of the heavier elements like oxygen and iron needed for planets and life
• its planet has to have liquid water
• a magnetic field to keep away cosmic rays