University of Queensland researchers have for the first time discovered terrestrial evidence of a metorite bombardment nearly four billion years ago.

It is widely accepted that the moon was heavily bombarded at this time, creating huge craters and basins.

But although the effect of these impacts is still clearly visible on the moon today, movement of the Earth's dynamic plates over geological time have reshaped the terrestrial surface dramatically, leaving little evidence of these catastrophic events.

In a paper published in the international journal Nature, UQ researchers report evidence of the oldest impact events so far discovered on Earth.

The research team of Dr Ronny Schoenberg, Dr Balz Kamber and Professor Ken Collerson of UQ's new Advanced Centre for Isotope Research Excellence (ACQUIRE) made the discovery by analysing 3.8 billion-year-old rocks from West Greenland collected by Oxford University collaborator Professor Stephen Moorbath and from Northern Labrador in Canada collected by Professor Collerson.

The researchers found these very old metamorphosed sedimentary rocks ­derived from the Earth's early crust ­contained anomalies in the isotope composition of the element tungsten.

"There is no plausible mechanism by which tungsten isotope anomalies could have been preserved in the Earth's dynamic crust-mantle environment. Therefore, we conclude these rocks must contain a compound derived from meteorites," Professor Collerson said.

Professor Ken Collerson www.uq.edu.au/uqresearchers/researcher/collersonkd.html

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