Without a protective layer of ozone, life would be exposed to DNA - damaging ultraviolet rays from the sun. (discovermagazine.com)
During the day, ultraviolet rays from the sun split oxygen, nitrogen, and other molecules in the upper atmosphere. (discovermagazine.com)
The humidity can be as low as 10 %, there are intense ultraviolet rays from the sun, and the high altitude can leave people short of breath. (scienceinschool.org)