Wendy Zukerman, Australasia reporter
A massive asteroid hit the Timor Sea around 35 million years ago - and the impact apparently contributed to the formation of the Antarctic ice sheets.
So says Andrew Glikson, a specialist in the study of extraterrestrial impacts, from the Planetary Science Institute at the Australian National University in Canberra, who analysed a dome found 2.5 kilometres below the Timor Sea, about 300 kilometres off Australia's north west coast.
Based on the structure of the dome, called Mount Ashmore, there were two obvious explanations for its formation: from a mud volcano or from the movement of tectonic plates.
But using a barrage of tests including scanning electron microscopy and seismic surveys, as well as chemical analysis of the rocks, Glikson concluded that the dome was the result of an asteroid crashing into the Earth at such speeds that it caused the Earth's crust to rebound (Australian Journal of Earth Sciences, DOI: 10.1080/08120099.2010.481327).
Images from scanning electron microscopy showed that the cracks and pulverised rocks throughout the dome were unlike those seen in tectonic plate movements.
Seismic section displaying chaotic deformation in the inner core of the Mount Ashmore structural dome.
Seismic surveys and above-ground magnetic studies revealed the dome's massive dimensions. Its diameter of over 50 kilometres and vertical axis several kilometres in height are significantly larger than previously found mud volcanoes - making this an unlikely candidate for one. So far the largest mud volcanoes, found in Azerbaijan, are only 10km in diameter.
According to ABC News, Glikson says the asteroid that created the dome was probably 5 to 10km wide.
"Smaller [asteroid] impacts only create an impact crater. But during larger impacts, something different may happen: an impact dome or central peak rises up in the middle of the crater."
In the case of Mount Ashmore, rock rebounded upwards at the point of impact, compensating for the huge compressive punch of energy delivered in collision.And when this asteroid collided with Earth, it wasn't alone.
"Several other craters have been documented from a similar time, including one of the Western Australian coast measuring 120km in diameter. Another asteroid impact structure in Siberia is 100km in size."
Glikson believes that this asteroid storm may have shifted the Earth's plates to create a gap between Antarctica and South America, known as the Drake Passage, which still exists today.
Discovery News writes:
"The rush of water through Drake Passage isolated Antarctica's climate from the rest of the globe, and fostered the growth of a large ice sheet."
According to Australian Geographic, these ice sheets in combination with newly-emerging currents around Antarctica may have allowed cooler water into the world's ocean, and possibly resulted in a well-documented cooling of the planet.