Almost exactly 37 years ago, on the morning of May 16, 1975, then 35-year-old Junko Tabei and her Sherpa guide Ang Tshering reached the 8,763-meter South Summit of Mount Everest — their final halt before pushing on to the 8,848-meter peak itself.

They made just enough room in the heavy snow to sit down. But when she realized what her next challenge would be, she shuddered with shock and anger, she says.

In front of Tabei, who had already cleared numerous danger spots while also coping with the physical and mental stresses of high-altitude climbing, was an icy, knife-edge ridge forming part of the border of Nepal and China.