Earth, moon were bombarded by asteroid shower 800 million years ago

Large craters on the surface of the moon suggests the Earth-moon system was slammed by an asteroid shower 800 million years ago, according to a survey published Tuesday in the journal Nature Communications.

Roughly 65.5 million years ago, a massive asteroid struck the Yucatan Peninsula. The violence of the Chicxulub impact is credited with triggering the mass extinction event that killed off the dinosaurs.

Scientists estimate such a violent collision is likely to happen just once every 100 million years.

On Earth, the remnants of asteroid impacts older than 600 million years have mostly been erased by erosion and volcanism, but on the moon, craters from hundreds of millions of years ago remain undisturbed.

To better understand the history of asteroid impacts on the Earth-moon system, researchers at Osaka University estimated the age of 59 large lunar craters using data collected by the Terrain Camera onboard Kaguya, a lunar orbiter launched by the Japanese Space Agency.

Scientists can estimate the age of large lunar craters by measuring the density of smaller craters inside. Analysis of the ages of the 59 craters, with diameters of 12 miles or more, showed at least eight were formed simultaneously.

Models accounting for crater scaling laws and collision probabilities determined the barrage of asteroids that scarred the moon were likely produced by a larger collision between Earth and a massive space rock — a collision 30 to 60 times more powerful than the Chicxulub impact.

The analysis suggests the collision immediately preceded the Cryogenian, a period of climatic and ecological upheaval that occurred between 720 and 635 million years ago.

Scientists suspect the disruption of a C-type asteroid triggered an asteroid shower that collided with the Earth-moon system around 800 million years ago.

It’s likely, researchers say, that such a bombardment deposited a large amount of phosphorus on the surfaces of Earth and nearby terrestrial surfaces, as well as dusted the lunar surface with volatile elements — residues that could be investigated by future moon missions.

“Our research results have provided a novel perspective on earth science and planetary science,” lead study author Kentaro Terada, professor of planetary science at Osaka, said in a news release. “They will yield a wide range of positive effects in various research fields.”

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