Research from The Australian National University (ANU) has identified one of the most extensive asteroid impact zones on Earth. The discovery comes in the lead-up to the passing of a 45-meter-wide asteroid very close to Earth this weekend.
Located in northeast South Australia, the East Warburton Basin contains evidence of a 30,000-square kilometre shock-metamorphosed terrain thought to have been caused by an asteroid measuring 10 to 20 kilometres in diameter that hit Earth more than 298 million years ago.
Dr Andrew Glikson, a visiting fellow in the ANU Planetary Science Institute and the ANU School of Archaeology and Anthropology, studied the impact of the ancient asteroid following an initial suggestion by Dr Tonguc Uysal of the University of Queensland.
“The size of the shock metamorphic terrain, larger than 200 kilometres in diameter, makes it the third-largest discovered to date on Earth,” Dr Glikson said.
“It is also possible that the asteroid impact dates back to the late Devonian period – 360 million years ago – a time of major mass extinction.”
Dr Glikson says research into past asteroid impacts is essential in the face of potential future asteroid encounters. This weekend, an asteroid – 2012 DA14 – will pass just 34,000 kilometres from Earth, potentially interfering with communication satellites. If the asteroid was to hit Earth, it would make a crater up to one kilometer wide, says Dr Glikson.
Dr Glikson believes that there may be a link between the East Warburton impact zone and another possible impact site, the West Warburton geophysical anomaly, located nearby.
“Asteroid impacts commonly occur in clusters of two or more projectiles. Where impacts are near-contemporaneous they are usually fragments of a larger body broken under the gravity effect of the Earth-Moon system.
Dr Glikson studied micron-scale features within quartz grains from sub-surface drill holes, using a three-dimensional optical microscope and a scanning electron microscopy. Dr John FitzGerald of ANU studied the features by Transmission Electron Microscope and Dr Erdinc Saygin studied deep seismic anomalies below the structure.
“These methods helped me to discover the impact site, which was buried under nearly four kilometres of younger sediments,” Dr Glikson said.
The finding follows the discovery of a 125-million-year-old impact structure 84 kilometres in diameter in southeast Queensland by Dr Glikson and colleagues.
The research is published on-line in Tectonophysics.