Well, there were, just no hominins. :-)
On 8/15/20 1:44 PM, Henry Spencer wrote:
On Sat, 15 Aug 2020, roxanna Mason wrote:
Think about deorbiting a stadium sized asteroid into a desert in the SW US or Sahara or Australia. It would break up and melt upon impact doing most of the work of disassembly.
Not that simple, alas. You need to somehow bring it in *slowly* for that to happen. At more typical impact velocities, the impacting body is largely vaporized; bits of it come down over a huge area surrounding the crater.
Daniel Barringer, the first to suggest that Meteor Crater was an impact crater (which is one reason why it's also called Barringer Crater), spent decades excavating and drilling for the huge mass of minable ore that he thought was underneath the crater. He never found it, because there's nothing there. (The Barringer family still owns the crater, but it's a tourist attraction rather than a mine.) The impacting object was a tiny fraction of the size he was expecting, and there are pieces of it strewn all over the US southwest.
That was (by current estimates) about a 50m object coming in at not much more than escape velocity. About half of it vaporized on the way down; most of the rest vaporized in the 10MT blast produced by the impact, which also excavated a 1200m crater. This would have been highly unpopular with the inhabitants of the region, had there been any at the time. :-)
Henry
