Why is life not possible on Venus and Mars?

Why is life possible of the earth?

Whay is life possible of the earth?

Why is it not possible to define total life of radioactive substance?

The earth would become so cold that life is not possible on it in the absence of the atmosphere. Explain why ?

How is our atmosphere different from the atmospheres on Venus and Mars ?

How is our atmosphere different from the atmospheres on Venus and Mars?