ABSTRACT
Parallel to the new and intensive Ries research with its interdisciplinary and international scope, impact research rekindled the discussion about the origin of lunar craters. In April 1966, a conference on 'shock metamorphism of natural materials' took place at the Goddard Space Flight Center with some ninety participants. Forty papers were presented. Bevan French had invited Wolf von Engelhardt to attend the conference and give a lecture on his work at the Ries crater. The international scope of the research by Engelhardt and his working group was much admired by those staying back in Tübingen. Chao ignored the Engelhardt working group completely, while El Goresy at least mentioned Hörz in the list of references, although not in the text itself. Chao's Ries engagement was part of his larger involvement with the USGS Astrogeology Group and NASA, so the Ries Crater was only one of several impact craters that he researched.
