Asteroids Battered Young Earth Longer Than Thought

This is a picture from the article of an artist's impression of a 6 mile wide asteroid striking Earth.  Some scientists believe that approximately 70 of these larger asteroids hit Earth between 3.8 and 1.8 billion years ago. 

 

The article entitled, "Asteroids Bettered Young Earth Longer Than Thought" gives insight about the asteroids that have hit earth.  One of the biggest periods of asteroids hitting Earth was the Late Heavy Bombardment, which occurred 4.1 to 3.8 billion years ago. Scientists debate what exactly happened during this era and how long it lasted, but they can agree on the notion that asteroids and comets pummeled the Earth, the moon, and the other terrestrial planets. Instead of researching craters, researchers decided to analyze spherules, or layers of rock droplets between millimeters to centimeters thick.  These spherules provide information about the impact even if the crater cannot be found.  Scientists can figure out the size and velocity of the asteroid, then go back to the earliest era of the Earth and figure out the number of asteroids that hit the planet.  Information has also been gathered concerning the evolution of life on Earth.  It is believed that asteroids introduced materials that helped simple life form on Earth.  They have also found a connection between crater sizes on ancient Earth and the sizes of asteroids in space.  William Bottke, a scientist at the Southwest Research Institute in Boulder, Colorado has investigated a possible missing source of asteroids that have impacted Earth along the inner edge of the main asteroid belt, also known as the E Belt.  Now unstable, this belt is thought to have held the asteroids that pummeled Earth during the Late Heavy Bombardment.  Different scientists have different theories about where the asteroids came from, yet is is inevitable that Earth has suffered many asteroid impacts dating back to at least 4.1 billion years ago, the start of the Late Heavy Bombardment. 

http://www.space.com/15424-asteroids-battered-earth-collisions.html