MONTREAL — The Artemis II mission is showing how even a short 10-day journey in deep space presents significant challenges to the human body, including exposure to radiation and other effects scientists are still studying.
The combination of radiation exposure, microgravity, and confined living conditions can place significant strain on the human body, said Dr. Farhan Asrar, a physician, space medicine researcher and associate dean at Toronto Metropolitan University’s School of Medicine.
The Artemis II mission marks a return to deep space for the first time in 50 years, offering a rare opportunity to closely monitor how astronauts are affected.
“There are still many effects of deep space on the body that we don’t fully understand,” Asrar said.
Radiation is the primary concern in deep space, Asrar said.
“Levels are higher than in low Earth orbit or on the (International Space Station), and it’s not just the amount — it’s the type.”
He explained that this form of cosmic radiation can affect cells, organs, and DNA differently than what astronauts experience closer to Earth.
“Some of these particles are more penetrating and potentially more damaging, which makes this mission a step into the unknown,” he said.
The space mission will provide data for scientists, despite its short length.
“Even short exposures can help us understand how the cardiovascular system, immune system, and even cognitive function might be impacted on longer missions,” Asrar said.
The mission, which launched earlier this month, is roughly four days into its 10-day journey. Its crew includes Canadian astronaut Jeremy Hansen, who will become the first Canadian in deep space, as well as American astronauts Reid Wiseman, Christina Koch, and Victor Glover. The team will circle the moon, which will be a first for space travel.
Every stage of the mission affects the astronauts’ bodies, Asrar said, adding, “It’s quite a disabling and extreme environment.” The most common side-effect tends to be motion sickness.
He noted that extensive training helps the crew manage these challenges.
“Many of them are also trained as pilots, which factors into how they handle symptoms and adapt to the conditions,” he said.
The mission also marks the first time a woman has gone into deep space, with Koch joining the flight. “The female perspective is a critical part of understanding how different bodies respond to deep space,” Asrar said. “We’ve never had a woman in deep space before, so this mission provides essential data for future exploration.”
Understanding these differences, believes Asrar, is not just about observation — it also informs how astronauts must care for their bodies during the mission.
Astronauts must rely on specialized exercise to stay fit in space, Asrar said, with about 30 minutes a day recommended for the Artemis II crew — far less than the up to two hours required on the International Space Station.
He said staying active is critical to slowing rapid muscle and bone loss in microgravity.
“Even a short mission can cause deconditioning if the body isn’t kept active,” he said, noting astronauts can lose up to one to 1.5 per cent of bone mass for each month spent in space.
During a live question-and-answer session with Canadian children, Hansen described one of the most noticeable effects of microgravity.
“I’m sure my face is a lot puffier now because there’s a lot more blood up in my upper regions of my body,” he said.
Asrar explained that the sensation is caused by fluid shifts that push blood toward the head in the absence of gravity.
“Without gravity pulling fluids downward, there’s increased pressure in the upper body, which can affect the eyes, sinuses, and balance,” he said.
Asrar added that these changes can also affect vision, kidney function, and the immune system, underscoring how even short missions trigger a cascade of physiological adjustments.
Beyond the physical strain, deep space missions also bring significant mental and logistical challenges. Astronauts must carefully manage limited food, water and medical supplies while living in tight quarters with little privacy, Asrar explained.
Asrar said team dynamics are crucial, as crews eat, sleep and work side by side throughout the mission.
“It’s important to have a team you want to be with and can work with, because literally 24/7 you’re together,” he said, adding that aside from the toilet, there are no real barriers separating crew members.
After returning to Earth, the crew will undergo rehabilitation to rebuild muscle strength, restore bone density and readjust to gravity. Asrar said tracking that recovery is just as important as studying the mission itself.
“The way the body adapts and re-apapts gives us critical information for designing countermeasures for longer missions,” he said.
He added that even a 10-day flight can provide valuable data on fluid shifts, cardiovascular changes and organ function, helping prepare humans for future missions to Mars and beyond.
The Artemis II capsule and its crew are scheduled to splash down in the Pacific Ocean off San Diego on April 10. Asrar noted that re-entry also places additional strain on the body.
“The forces during re-entry can be strenuous,” he said, “and the body needs time to readjust to gravity.”
This report by The Canadian Press was first published April 5, 2026.
Charlotte Glorieux, The Canadian Press
