A new study is challenging the longstanding theory that Earth formed in a pinball fashion, through random collisions of rocky stellar bodies that crushed together through gravity. The water we enjoy would have collided at random, too, when one or more comets smashed into the growing planet, the old theory says.
“If that is how Earth was formed, then it is pretty lucky that we have water on Earth,” says Martin Schiller, an associate professor at the University of Copenhagen, in a press release. “This makes the chances that there is water on planets outside our Solar System very low.”
