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Asteroids Battered Young Earth Longer Than Thought

A giant ancient barrage of asteroids striking Earth may have lasted much longer than previously thought, with some collisions perhaps even rivaling those that created the largest craters on the moon, researchers say.

Scientists think untold numbers of asteroids and comets pummeled Earth, the moon and the inner planets during an era known as the Late Heavy Bombardment about 4.1 billion to 3.8 billion years ago. Investigators continue to debate the precise nature of this epoch in terms of what happened and how long it lasted.

To learn more about the Late Heavy Bombardment, scientists would like to analyze the most obvious evidence cosmic impacts leave behind, their craters. However, while such craters are preserved well in the vacuum of the moon environment, they disappear quickly on Earth due to erosion and tectonic activity.

Instead, researchers analyzed other evidence of asteroid impacts — millimeter- to centimeter-thick layers of rock droplets known as spherules.