Multiple Cosmic Impacts Slammed Earth 790000 Years Ago

Scientists have learned a bit more about the history of cosmic impacts on Earth. They've found that 790,000 years ago, there were multiple cosmic impacts on our planet with global consequences.

In this latest study, the researchers dated so-called tektites from various parts of the world. These tektites are actually rock glasses, which originated during impacts of asteroids or comets. The researchers used a dating method based on naturally occurring isotopes that allowed them to date the tektites more accurately than ever.

"That's how we know when, where and how often projectiles struck Earth, and how big they were," said Mario Trieloff, one of the researchers, in a news release.

There have been signs that a major impact took place about a million years ago. Now, though, researchers have gotten a closer look at this event. By examining the tektites, the researchers found that there must have been a cosmic impact about 793,000 years ago, give or take 8,000 years. Not only that, but the researchers found many tektites around the world dating from the same time; it's likely that multiple cosmic impacts took place at the same time.

The consequences of these impacts were dire; at the local level, there was fire and earthquakes for hundreds of kilometers surrounding the impact site. An ocean impact would have caused tsunamis hundreds of meters high. At the global level, dust and gases were ejected into the upper levels of the atmosphere, blocking sunlight and lowering surface temperatures. Biomass production was also affected, though did not result in global mass extinction as in the case of the dinosaurs 65 million years ago.

The findings are published in the journal Gechimica et Cosmochimica Acta.

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