Computer simulation suggests early Earth bombarded by asteroids and comets

A team of researchers at the Southwest Research Institute in Colorado has created a computer simulation that depicts the first 500 million years of Earth's existence, taking into account collisions with asteroids and comets. In their paper published in the journal Nature, the researchers describe how they built their simulation using crater data from the moon and other planets, and what it likely meant for early Earth.

The general consensus among planetary scientists is that Earth was formed approximately 4.5 billion years ago—unfortunately, because our planet underwent such upheaval during the next half billion years or so, little has survived that can be used as evidence to offer a picture of what the planet looked like and what the impact of events during that time mean for the world we see today.

To gain a better understanding of the time after the Earth was formed, known as the Hadean Eon, the researchers looked to other bodies in our solar system—the moon in particular. The cratered face of our solitary natural satellite suggests a violent past, which offers hints of what our own planet endured. The researchers also noted the amounts of minerals that attach to such elements as gold present in the Earth's crust, material believed to have come from other celestial bodies.

After putting all the data into their model, the simulation showed that Earth, in addition to being struck by many small to medium sized asteroids, was also likely struck by several really big ones, big enough to melt the entire surface of the planet—which would explain the lack of rocks from that time surviving to modern times. This suggests that Earth's surface was melted and buried over and over again, though there were also likely long respites in-between.

The simulations also indicate that if life existed during the Hadean Eon, it would have had to have been deep in the Earth's crust and resistant to heat. Also any water on the surface near big impacts would have been vaporized and sent into the atmosphere, where it would have stayed for a period before eventually falling back to the surface.