Giant asteroids reshaped Earth 4 billion years ago

geek.com

The solar system used to be a much rougher place than it is today. That much we already knew, but a new model developed by an international team proposes a considerably more violent early life for our planet than anyone suspected. This new study describes an Earth that was frequently struck by massive asteroids that melted and mixed the surface multiple times, ultimately shaping the planet we know today.

This model differs from past version of the early, or Hadean Earth 4-4.5 billion years ago. The established wisdom is that Hadean Earth (which means hell-like, if you needed a better visual) was largely molten because of volcanic activity and was frequently struck by smaller asteroids. According to the new study, lunar and terrestrial geological data suggests Earth was struck repeatedly by objects over 300 miles in diameter. If something that size hit us now, it would be game over for virtually all life.

The team says that during this 500 million year period the planet likely experienced three to seven impacts by objects more than 300 miles wide. There were also as many as four impacts by titanic space rocks more than 600 miles across. If there had been any life on the Earth, a 600 mile wide monster asteroid probably would have wiped it out. Surprisingly, these impacts are compatible with the existence of liquid water on the surface as early as 4.3 billion years ago.

The accepted model right now says that Earth’s current mass is less than 1% due to impact events in its early history, but that number could go up a bit if this new model is accepted. Impacts of this size may have had profound effects on the formation and behavior of the tectonic plates and volcanism of the planet. This research could be the piece that bridges the gap between the Earth’s formation and the impact that likely created the Moon (and the planet as it now exists).