Why do you think that on other planets there is no atmosphere? It all depends on the conditions on the planet. I do think that if on the planet there are appropriate conditions for life then it must appear the life. Planetary scientists, examined the chemical composition of rocks of Mars, in 2013, stated that 4 billion years ago on the red planet had the same amount of oxygen as on Earth. Planet Kepler 22b, This planet on which life can be. Because the surface temperature is about 25 °C despite the fact that the star is weaker than our Sun 8 times, but the planet is much closer to her. Is the planet in the constellation Sail in 36 light years from us. Planet Kepler 22b is Very distant planet at a distance of 620 light years. The temperature of the planet is consistent with the average temperature at resorts in Greece, only the structure is more reminiscent of Neptune, consists mainly of a vast ocean, so if there is life, in the aquatic environment. And such planets can be a lot. Recently been discovered presumably from 6 planets suitable for life