Earth was pounded with meteorites for 85 million years – just as complex life was getting started, according to new research.
It would have triggered tsunamis and widespread wildfires and changed our planet’s chemical make-up forever.
The finding is based on an analysis of almost 60 craters at least 12 miles wide on the moon.
They were caused by an asteroid about 62 miles in diameter that broke up – bombarding both worlds.
It may have been carrying phosphorous – a vital building block for life.
Earth was showered with 110 million billion pounds of debris – up to 60 times more than the city sized space rock that wiped out the dinosaurs.
It happened some 720 to 635 million years ago as land plants were taking hold – and the first multi-cellular animals were evolving.
Lead author Professor Kentaro Terada, of Osaka University, said: “This was immediately before the Cryogenian – which was an era of great environmental changes.”
His team used images from the Terrain Camera (TC) on board the Japanese Space Agency’s lunar orbiter Kaguya.
The relentless bombardment described in Nature Communications could have kick-started life on Earth.
A thin layer of the rare Earth element iridium has been detected worldwide in rocks dating back 66 million years.
This is evidence of the six mile wide asteroid that smashed into the Gulf of Mexico near the town of Chicxulub.
It caused the Cretaceous mass extinction of three-in-four land animals – including the dinosaurs.
Prof Terada said: “The probability of an asteroid of this size striking Earth is thought to be once in 100 million years.”
Impact craters on Earth created before 600 million years ago have been erased over by erosion, volcanism and other geologic processes.
So to find out about ancient meteorites his team investigated the moon where there is no weathering or erosion due to its lack of an atmosphere.
Prof Terada and colleagues discovered eight out of the 59 craters they looked at were formed simultaneously – including the dramatic 60-mile wide Copernicus.
They based their results on radiometric dating of ejected material from Copernicus and information obtained from glassy beads collected during the Apollo missions.
Prof Terada said: “The moon experienced an asteroid shower approximately 800 million years ago.
“As an asteroid shower took place on the Moon, a similar event must have occurred on Earth.”
The researchers turned to crater-scaling laws to work out roughly when the deluge happened.
Prof Terada said: “Based on collision probabilities, meteorites with a total mass about 30 to 60 times the one responsible for the Chicxulub impact collided with the Earth just prior to the Cryogenian period – approximately 720 to 635 million years ago.”
Though nowhere near as abundant on Earth as carbon, hydrogen or oxygen, phosphorous is one of the key elements to life on our planet.
Prof Terada said: “An asteroid shower may have brought a large amount of phosphorus to the Earth – affecting the terrestrial surface environment.”
It helps form the backbone of the long chains of nucleotides that make up DNA – the building blocks of biological life as we know it.
Phosphorous is also vital to cell membranes and the cell energy-carrying molecule ATP.
It’s been suggested for years that the chemical likely came to Earth aboard meteorites.
Prof Terada said: “Understanding meteoroid bombardment of the Earth system is an issue of both great scientific interest and practical importance because impacts are potentially hazardous to the Earth.”
The Cambrian explosion, a rapid evolutionary event that resulted in the divergence of major animal groups, happened 541 million years ago.
Since then at least five mass extinctions have occurred – with asteroid impacts considered a major cause. But they can be good for life – as well as bad.
Prof Terada said: “Lunar crater chronology provides new insight into external forcing from asteroids that might have driven ecosystems towards larger and increasingly complex organisms after 800 million years ago.”