the Earth you walk on today might not be the same planet that was born 4.5 billion years ago. Many scientists believe that in its infancy, Earth collided with another world the size of Mars, and that instead of being destroyed, it was transformed, incorporating the mass of that foreign body to become the planet we know. Recent research adds another layer of relevance to that hypothesized cosmic event: Scientists believe that without that other body, the basic conditions for life to emerge on Earth might never have appeared.
A team from the University of Bern in Switzerland argues that, due to its proximity to the sun, the proto-Earth that