s70-56407

S70-56407 (December 1970) --- Astronauts Richard F. Gordon Jr., left, and Harrison H. Schmitt ? backup crew members for the Apollo 15 mission -- get ?feet-on? experience with an a'a' lava flow during geology training in Hawaii. A?a? is the most common appearance type of lava flow that cools down, to form fragmented, often spiny or rough surfaces. Photo credit: NASA