Comment by markovs_gun

Gravity is a pretty major benefit for the development of complex life, because low gravity cannot form an atmosphere, and without an atmosphere, radiation would cause massive problems for early lifeforms. As bad as radiation is for existing life on Earth's surface today, I imagine it would be far worse for complex macromolecules to form when getting bombarded with radiation constantly. Temperature is also a problem without an atmosphere- you would tend to have extreme temperature cycles. Not insurmountable, but definitely more difficult to make it work. Given the sheer unlikelihood of life developing in the first place even in fairly good conditions like on Earth, I feel like it's a lot less likely on an even harsher environment like an asteroid.