28 Jan
2009
28 Jan
'09
4:15 p.m.
More from the depths of my memory. A water drop into a film, on a flat surface, will rebound in a ring, rather like a crown. No peak. A water drop into a deep puddle, will rebound a drop back up. Peak. So I'm surmising that you will get a central peak in a crater if the structure of the ground at ground zero has the proper rebound characteristics. This is probably at least as important as mass of the impactor. Also remember that many craters on the moon have been flooded with lava since they first formed. Some of them with central peaks had the peaks completely covered. They are still there, but buried under a sea of frozen lava.