Astronauts Ken Mattingly and Neil Armstrong. They are shown studying geology in Iceland. Note the geologic hammer carried by Mattingly.
NASA
1967
<a rel="nofollow" class="external text" href="https://history.nasa.gov/EP-95/crew.htm">EP-95 ON THE MOON WITH APOLLO 16</a>, <a rel="nofollow" class="external text" href="https://www.hq.nasa.gov/office/pao/History/alsj/a11/images11.html">Apollo Lunar Surface Journal</a>, <a rel="nofollow" class="external text" href="https://www.dvidshub.net/image/714484/iceland-geology-trip-note-void-s67-38404">DVIDS</a>