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One-Two Punch

StarDate: 
May 30, 2015

Like a boxer getting pummeled by his opponent, central Australia may have taken a one-two punch from a pair of space rocks at least 300 million years ago. If so, they’re the biggest punches yet discovered.

On the cosmic timescale, Earth gets punched pretty often. These impacts by large asteroids can wipe out much of the life on Earth. An impact about 65 million years ago, for example, may have helped kill off the dinosaurs.

Rain, wind, and the motions of Earth’s crust have erased many of the craters that these impacts created. But evidence of the impacts can be buried far below the surface.

That’s the case in Australia. Rocks pulled from many miles deep revealed that grains of quartz were cracked by a massive impact. Seismic waves, as well as readings of the magnetic and gravitational fields, revealed bulges of dense volcanic rock even deeper. The entire field spans more than 250 miles.

From those lines of evidence, researchers concluded that twin asteroids hit that region at least 300 million years ago. Each asteroid was several miles in diameter. When they hit, they likely would have killed life across much of the planet.

The impacts penetrated deep into the crust. The layer below the crust rebounded, pushing up molten rock that created the dense bulges seen today.

Many questions about the possible impacts remain unanswered. Yet there’s good evidence that Australia took a strong one-two punch hundreds of millions of years ago.

 

Script by Damond Benningfield, Copyright 2015

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