South Africa: Meteorite Find Has Scientists Salivating
Business Day (Johannesburg)
Scientists have discovered a piece of a giant meteorite that hit what is now Limpopo 145-million years ago, offering a tantalising glimpse of what was happening in our solar system at the time.
The object has triggered such interest that it has been flown to London to be exhibited at the city's Science Museum for the next few months.
The 25cm meteorite was discovered by an international team of geologists in a frozen magma pool at the bottom of the massive 70km-wide Morokweng crater, west of Vryburg.
It is the first time scientists have found a large meteorite fragment in such a large crater, said Marco Andreoli, scientist at the South African Nuclear Energy Corporation and co-author of a paper describing the discovery published this week in the international science journal Nature.
"Nobody had even considered the possibility of finding such a large pristine meteorite fragment," as scientists had previously thought that any asteroid capable of creating such a big crater would have been travelling so fast that it would have been melted or vaporised on impact, he said.
The discovery of the beach-ball-sized meteorite suggests the giant asteroid may have hit the earth at a lower speed than had previously been assumed, he said. Another intriguing possibility is that it was trailing behind the main asteroid.
The meteorite's composition has also got scientists excited. It has less iron or nickel than other meteorites, and is more radioactive elements such as thorium and uranium. That suggests the asteroid came from a different source to other objects found on earth so far, said Dr Adrian Boyce, a senior research fellow at the Scottish Universities Environmental Research Centre.
The scientists discovered the meteorite fragment while assisting junior exploring company Business Venture Investments 33 hunt for copper and nickel in the Morokweng crater, said Andreoli.
"It was a huge stroke of luck, as had the (prospecting) bore-hole been sited just a metre away, it might have missed the meteorite altogether," said Iain McDonald of Cardiff University's School of Earth, Ocean and Planetary Sciences.
Most meteorites found to date have been in Antarctica or deserts, as the climate in these regions helps preserve the objects. In addition to the Morokweng meteorite crater, SA is also home to the world's largest and oldest crater -- the 2-billion-year-old Vredefort Dome, which spans 380km.http://allafrica.com/stories/200605120348.html