Apollo 16 astronaut John Young is trying to find a suitable rock sample. He has his hammer at the ready. He will place the gnomon in position near the selected rock so that the rock and the gnomon, and its cast shadow, will be included in two photos he will take before picking up the rock. The second photo is taken a few steps to the right or left of the first photo to provide a stereoscopic pair. Another photo will be taken after the rock is collected to document which of the rocks in the field of view of the first two photos is the one selected for return to Earth. This careful photographic documentation will allow scientists on Earth to know the exact orientation of the rock when they test for certain important geologic properties such as residual magnitism or impact from solar wind particles.

John does not want to use the hammer to knock a small piece off a big rock because that is hard work, it takes valuable time, and uses up energy. It is much better if he can find a suitable fragment nearby that has been knocked off the big rock as it was ejected from the crater a billion or so years ago by meteor impact.

Geology was a whole new world for us pilots with its unfamiliar language and techniques of investigation. It was interesting but difficult to learn, as we were focused on mastering the knowledge and skills for safely flying the command module and lunar module to the Moon and back.

To be the beneficiary of all this wonderful education and training - what an opportunity and experience. I feel blessed every single day.