[blam]

The Arizona impact occurred 50,000 years ago.

[Mitchell]

I did a little more research on this, and it turns out that there's quite a bit of uncertainty in the date. NASA says it occurred sometime between 50,000 and 20,000 years ago. See this page at the JPL Near-Earth Object Program. That web page also gives 80 feet as the diameter of the object that hit, a little smaller than 100-meter figure from the other website I quoted above.

Thanks for bringing this out.