Question

why life is possible on the Earth

Answer 1

Life as we know it is possible on Earth because of its distance from the sun, allowing water to exist in all three states, and in a cycle. If we were closer to the sun (but not as close as Venus), life may still have evolved, but very differently, likewise if we were a little further away.

Answer 2

Life is possible on planet Earth only. Among all planets it is the only planet at the suitable distance from the sun. Due to this, it has a moderate temperature which makes life possible on earth. It has water present on it.  The atmosphere protects us from harmful ultra-violet radiation from the sun. It has many gases which are essential for us.