Had Earth been smaller - no plate tectonics = no life?
Earth: A Borderline Planet for Life?
Our planet is changing before our eyes, and as a result,
many species are living on the edge. Yet Earth has been
on the edge of habitability from the beginning.
New work by astronomers at the Harvard-Smithsonian
Center for Astrophysics shows that if Earth had been slightly
smaller and less massive, it would not have plate tectonics -
the forces that move continents and build mountains. And
without plate tectonics, life might never have gained a
foothold on our world.
Full article here:
http://www.physorg.com/news119108915.html