Velocity matters.....
<So this asteroid is now known to be 5 miles in diameter and would produce a crater 20 x 5 miles in dia on earth, if it hit - i.e. 100 miles. Not a patch on Chixulub but it would cure gridlock in LA in a moment!
Heh, or rinse that growth off the east cheek of Australia. Surfs up mate!
About the 20 x 5 mile crater guess. Thats an interesting rule of thumb but what density, relative velocity and range of inclinations is assumed?