Saturday 21 October 2017

Earth was regularly pummelled by asteroids that left giant craters on moon - Trinity researchers

Planet Earth
Planet Earth
Allison Bray

Allison Bray

A team from Trinity College has unearthed literally ground-breaking new research suggesting that Earth shares more similarities with other planets than previously believed - and was regularly pummelled by asteroids that left giant craters on the moon.

A study of the oldest pieces of rock on Earth known as zircon crystals by a team of researchers at the School of Natural Sciences at Trinity College found that the prehistoric crystals were probably formed after fiery meteorites known as bolides crashed violently into the Earth from space more then four billion years ago.

The collisions caused the Earth’s crust to melt and form giant pools of molten rock about four kilometres thick that left massive craters in various locations around the world, including the largest Vredefort crater in South Africa, which measures 300 kms.

The second largest and best preserved crater, believed to be about two billion years old, is the Sudbury impact crater or Sudbury Basin,  measuring 250 kilometres, which encompasses the remote mining town of Sudbury, Ontario, about 350 kilometres north of Toronto, Canada.

But what the four-person team found after they travelled to the Sudbury Basin  is believed to be truly ground-breaking.

It was previously thought that the tiny zircon crystals, which measure around the width of a human hair, were formed due to the shifting of tectonic plates – giant slabs of rock in the Earth’s core that have been clustering together and breaking off like bumper cars hitting each other  for millions of years.

But after studying thousands of crystals taken from the Sudbury Basin in 2014 and comparing them with zircon crystals found in Australia believed to be more than four billion years old,  the team discovered that the Sudbury crystal compositions “were indistinguishable from the ancient set.”

Lead researcher Gavin Kenny, whose findings have been published in the academic journal “Geology” said:

“What we found was quite surprising. Many people thought the very ancient zircon crystals couldn’t have formed in impact craters, but we now know they could have.”

“There’s a lot we still don’t fully understand about these little guys but it looks like we may now be able to form a more coherent story of Earth’s early years – one which fits with the idea that our planet suffered far more frequent bombardment from asteroids early on than it has in relatively recent times.”

Intriguingly, their research suggests that Earth shares similarities with the moon, whose dark spots visible from Earth  are impact craters, as well as planets in the solar system like Mercury, which is also peppered with craters.

“It makes more sense that the Earth looked like Mercury and that we share more of a similarity with other planets,” he said.

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