Asteroid impacts 3.3 billion years ago may have boiled the oceans

Science Focus

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The chaos in the early Solar System was fiendish. Even after the planets had coalesced, there was more than enough rubble left behind to cause frequent and violent impacts that would have rocked the Earth’s youthful crust. After a phase of intense bombardment between about 4.1 and 3.8 billion years ago, things on the asteroid collision scene calmed down. Relatively speaking…

We don’t know exactly when life first developed on Earth, but we know it was present by 3.4 billion years ago. We don’t know if life was present to suffer from the earlier period of bombardment, but we know it was around for any impacts that followed. So what kinds of extraterrestrial punches did life take after 3.4 billion years ago?

A new study by Stanford’s Donald Lowe and Louisiana State University’s Gary Byerly examines a fascinating record of major impacts in South African rocks around 3.3 billion years old. Eight impact layers have been identified in these rocks, each containing sand-sized blobs of rock that solidified after the impact vaporized bedrock. The layers also show signs that they were hit by tsunamis shortly afterward.

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