Astronaut Chris Hadfield spoke Saturday morning at the University of Calgary to share his experiences of living in space for five months.

It was Hadfield's first public presentation since his return to Earth in May and the retired colonel took the time to answer questions from children and adults alike.

Many of the questions focused on the curious physical effects of being in space: What happens when you sneeze? What happens to your bones?

However, others veered into more serious territory, with Hadfield explaining how it feels to prepare for a trip you might not return from.

Hadfield spent several years before blastoff making sure to do the things he wanted and saying goodbye to friends and family.

"That way, the biggest emotion in blastoff is relief," he said.

There were also plenty of questions about what it takes to be an astronaut.

In Hadfield's words, it takes three things — outstanding physical health, the ability to learn complex concepts quickly and strong decision-making skills.

Roughly 70 per cent of applicants for astronaut jobs are eliminated because of health concerns, he said.

Hadfield was the first Canadian to command the International Space Station. With the help of his son, Evan, Hadfield built a huge presence on social media through a host of tweets, photos, videos and interviews.

On Friday, he was also parade marshal for the 101st Calgary Stampede.

Hadfield returned to Earth in May aboard a Soyuz capsule and landed in the steppes of Kazakhstan.