One-Two Punch

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