Collisions with large objects from within the solar system have occurred throughout Earth’s history. These impacts result directly from the processes that formed the Sun and planets. Many large collisions (in the first few hundred million years of Earth’s existence) liquefied the top couple of miles of our planet’s surface, sterilizing any life. Yet this era of bombardment actually prepared the way for advanced life by dramatically reducing the material in the solar system that could collide with Earth during the last 550 million years when multicellular life exploded onto the scene. Check out this previous post to see how these bombardments benefited life.

• “Late Heavy Bombardment: Not So Sterile”