We have found evidence of ancient impacts all across the Earth, from the famous Chixulub crater in Mexico to the Sudbury Basin a little bit closer to my home.  From Space the remains look nothing like craters, millions of years of sediment and growth hide the massive regions from obvious detection, but signs remain of these massive events, even after millions of years.  This week, what is possibly the largest impact crater basin ever discovered has been found in central Australia.  And it is thought to originate from the breakup of a massive 400 Km asteroid into two pieces that...