As one of their instructors put it: “The canyon was a good place for them to get their feet wet in geology, for there is such a well‐exposed sequence of structured rock there.”

The somewhat footsore astronauts made the trip back up the canyon by mules

For their second field trip, the astronauts were taken in a boat to the Marathon Basin in West Texas, which has one of the most complicated geological structures in the nation.

They were also taken to the Big Bend National Park in West Texas for observations of volcanic rock, such as they may encounter on the moon.

On the their third trip earlier this month to the Kitt's Peak Observatory, the astronauts spent from midnight until five in the morning studying a telescopic image of the moon as geologists pointed out geological aspects of the moon and the kind of features they want the astronauts to look for as they approach and land on the lunar surface.

The astronauts were then taken on a flying trip over the Meteor Crater near Flagstaff and on a walking trip to the nearby Sunset Crater to observe a relatively new volcanic formation.

The purpose was to teach the astronauts to distinguish between craters caused by meteorites and those caused by volcanoes, and thus help settle the scientific argument over whether the craters in the moon have been created by meteorites or volcanoes or both.

The present 58‐hour course is the first of four planned for the astronauts, or at least some of them.