Natural glass, found only in Australia, could be evidence of the impact of unknown ancient asteroids, researchers say.
A new analysis of “tectite” that created shocks point to a powerful conflict that casts the remains of southern Australia millions of years ago. Scientists are still searching for impact craters.
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Tektites creates naturally formed glasses when metstones collide with the Earth and throw molten surface rocks in all directions. Most techtites come from one of five major splash zones, including those that spread debris into Australia and Southeast Asia almost 800,000 years ago.
In 1969, researchers studied techtites from this Australian field. Most of the glasses had a similar composition, but some seemed old and chemically different from others. A 1999 study found that the strange techtites were millions of years old, but previous estimates had considerable wiggling room and there was not enough information to determine whether the strange rocks formed with different, large influences.
Now, in a new study published in the Earth and Planetary Science Letter on August 29, scientists measured the density and magnetic properties of thousands of techtites in the South Australian Museum collections collected from the area. They brought 417 unusual samples to France and after further investigation they identified six techtites that had the same chemical structure as the unusual techtites that had been studied decades ago.
The team determined that techites differed sufficiently for most ages and composition of the other techites in the regions most likely not formed by the influences that created the Australian techite field. Instead, they could be from previously unknown influences that occurred almost 11 million years ago.
“These little glasses are like small time capsules from deep in the history of our planet,” Jordan said.
The team was called the Tektites of this ancient shock “Ananguite”. Some of the techtites landed at the home base of the people of Pitjatjara and Yankunytjatjara.
“What further intrigued the discovery is that, while the impact must be immeasurable, scientists have yet to find the crater,” Jordan said. Although no craters of the right age are known nearby, the team proposed several possible sites in the Philippines, Indonesia and Papua New Guinea. In volcanic regions like Papua New Guinea, impact craters may have been mistaken for volcanic features or may have been obscure for years.
Findings may show scientists that the Earth may give better ideas at a frequency of extreme effects, and that the effects large enough to produce techtites are more common than previously thought.
“Understanding when and how often a large asteroid hit Earth can also help us assess the risk of future impacts, which is important for planetary defense,” Jordan said.
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