Solar system’s biggest impact scar discovered - MIT News Office
Until now, nobody had clearly identified signs of any ancient impact in that size range. There are one or two even larger impacts thought to have occurred in the early solar system, a controversial theory that there was one on the innermost planet Mercury, and a widely accepted one that the Earth was struck by a planet as big as Mars, melting the crust and ejecting it into space where some of it clumped together to form our moon.
