New Scientist details a pretty awesome collision in space:
At roughly 8500 by 10,600 kilometres across, it is nearly 15 times the area of the Moon’s South Pole-Aitken basin which, at 2500 kilometres in diameter, is the largest undisputed impact scar in the solar system.
The Mars crater was probably created by an object as large as 2700 kilometres across – over half of the diameter of Mercury. The effects of such an impact would have been catastrophic, says Andrews-Hanna.
“Within the basin you’d have had a magma ocean – it would have been easily several tens of kilometres deep,” he says. “Outside the basin you would have had a tremendous amount of ejecta raining back down on the surface.”