This great video highlights one of the reasons we send astronauts underground in caves: to prepare for life on the International Space Station. More info: http://www.esa.int/Our_Activities/Human_Spaceflight/Caves/Why_caves
Ascending the sheer face of a mountain cliff takes physical stamina and mental toughness; imagine what it takes when you’re more than a million feet above sea level, and the mountain is moving more than five miles a second? Welcome to spacewalking on the International Space Station! These images were captured during spacewalks performed by NASA Astronaut Jeff Williams and Kate Rubins in August and September 2016.