Artist's impression of an asteroid in front of Earth (Image: Getty Images)From the article...
EVIDENCE OF A MASSIVE crater, at least 50 km across, has been discovered under the Timor Sea and may help scientists explain a rapid cooling of the planet 35 million years ago.
The new findings, announced today and published in the Australian Journal of Earth Sciences, suggest that the impact could have contributed towards the formation of the Antarctic ice sheet.
When Dariuz Jablonski, an oil exploration geologist with Finder Exploration, was conducting seismic surveys in the Timor Sea north of Broome in Western Australia, he found what he suspected to be the remains of large crater site. Dariuz asked Dr Andrew Glikson of the Australian National University in Canberra to help investigate.
Andrew, a specialist in extraterrestrial impacts, conducted tests on rock specimens from the sea floor. He found structural features which suggested great heats and pressures and he concluded that the area was the raised “dome” of a crater produced by an asteroid collision 35 million years ago.
"The identification of microstructural and chemical features in drill fragments taken from the... drill hole revealed evidence of a significant impact," he says.
The minimum size of the dome, which "represents elastic rebound doming of the Earth crust triggered by the impact" is 50 km across, but the full size of the crater could be significantly larger, he told Australian Geographic. "It would be possibly 100 km.”
From the probable diameter of the crater, Andrew estimates that the asteroid which struck the Timor Sea was between 5 and 10 km in size.
Correlation with global cooling
This impact coincided with a time of heavy asteroid bombardment globally. Several other craters have been documented from a similar time, including one off the WA coast measuring 120 km in diameter. Another impact structure in Siberia was created by an asteroid 100 km in size.
Andrew believes that collisions such as this may have played a role in the rapid decline in global temperatures. He says that the onslaught of numerous asteroids shifted the Earth's plates to create a rift between South America and Antarctica known as the Drake Passage, which still exists today.
“It allowed the circum-Antarctic ocean current, a cold current, to be established — this allowed the Antarctic ice sheets to form,” he says. These ice sheets, along with the newly established circular current around Antarctica, forced cooler water into the world’s ocean and may have resulted in a well documented cooling of the planet.
Link: Journal Article
Link: Australian Journal of Earth Sciences An International Geoscience Journal of the Geological Society of Australia
Link: ANU News Release