What does the Qur’ān say about life on other planets and stars?
There are subtle references in the Qur’ān which indicate that earth is the only planet in this universe where there is life. Consider, for example, the following verses which describe the creation of matter as a passing reference:
Say: is it that you deny Him who created the earth in two days and do you join equals with Him? He is the Lord of all the worlds. He set on it mountains standing firm, high above it and bestowed blessings on the earth and measured therein all things to give them nourishment equally for all the needy. All this took four days. Then He directed His attention to the sky [ie this universe] and it was in the form of smoke at that time and said to it and to the earth: Obey are commands willingly or unwillingly. They said: We are present [before you] in willing obedience. So He completed them as seven heavens [universes] in two days and revealed to each heaven its duty. (41:9-12)
These verses show that at the time of creation of our universe, it was only our own earth which was given the characteristics which were conducive to life. Allah (swt), however, knows best.
The Qur’ān also says that there are seven universes and each universe has an earth:
Allah is He who created seven universes and of the earth a similar number. His directives keep descending in them. (65:12)
It is likely that in each of these earths there is life, since there is in one of them.