A Chicago native, Watney attended the University of Chicago for his undergrad before moving on to Northwestern University where he earned a Ph.D. in Plant Biology and Conservation with an emphasis in hydropedology and environmental engineering. While a graduate student, he had his first experience with NASA by becoming a research fellow with the Graduate Student Researchers Program (GSRP). His work focused on hydrologic flow paths and sustainable water resources management within the Earth's Critical Zone.
Mark then spent two years in the Peace Corps engineering sustainable agriculture and water irrigation systems for developing nations.
Upon returning, he applied to the NASA Astronaut Candidate Program and was selected for his outstanding academic accomplishments, dedication and service to the community, and an exemplary record of professional achievement.
Mark Watney was then chosen for the Ares III mission because of his humor and good attitude. Mark Watney was also selected to perform experiments on plant growth using Martian Soil and Martian gravity. Mark Watney was also chosen to use his experience with plant growth to research the possibility of colonizing Mars, sometime in the near future.
After flying out of Mars' atmosphere near the end, Watney mentions he has chest pain, probably because the G-forces broke some of his ribs. This is no doubt due to spaceflight osteopenia, a condition where the bones become less dense after spending longer periods in low or zero gravity. Since Mars' gravity is only 38% of that on Earth, Watney's extended stay has caused his bones to become brittle, possibly worsened by lack of vitamins and minerals from food. The subdermal hemorrhages seen on his back may also be the result of vitamin shortage, especially vitamin K, which potatoes only provide in very low quantities.