Artemis astronauts will face big physical challenges as they deal with Earth’s gravity again: ‘Almost impossible to walk in a straight line’

They won’t be “over” the moon even after returning from it.

Following their historic 10-day flight around the moon, the intrepid Artemis II astronauts are slated to return to Earth Friday evening, marking the end of the United States’ first lunar foray in over 50 years.

But they won’t be out of the woods yet — the moonstruck space explorers will have to deal with a precarious splashdown and a host of residual health effects.

“With eyes closed, it was almost impossible to walk in a straight line,” NASA astronaut Andreas Mogensen previously said while recalling the side effects following a 200-day stint in space in 2024 as part of NASA’s SpaceX Crew-7 mission.

The Artemis II crew — comprised of Reid Wiseman, Victor Glover and Christina Koch ⁠and Canadian astronaut Jeremy Hansen — is currently approaching the critical and highly dangerous point in the journey where they’ll be reentering Earth’s atmosphere at 25,000 miles per hour on Friday, April 10.

Their survival will depend on Orion’s 16½-foot-wide heat shield, which will have to endure temperatures of 5,000 degrees Fahrenheit. This is a precarious prospect, given that the fire forcefield is a dead ringer for the component present on the uncrewed Artemis I, which returned damaged with a chunk missing from it.

Happy water landings

If all goes well during the trip, which marks the furthest humans have ever flown from Earth at over 252,756 miles, the Orion will be descending under parachutes before splashing down that same day at 8:07 EST off the coast of San Diego, Fox News reported.

Upon arrival, the astronauts will power down the spacecraft, after which their retrieval is in the Department of War’s hands.

“Then that’s where my job comes in, of recovering the crew module alongside all the other NASA and Amentum employees we have on the ship,” said Jason Endsley, the lead ground instrumentation engineer with Amentum, NASA’s advanced engineering partner, which presides over the retrieval.

This means outfitting the Orion with a special stabilizing collar to keep it upright in oft-tumultuous seas — although the forecast is clear for the time being.

After popping the hatch, the crew will be assessed by US Navy medical personnel and assisted by recovery divers onto an inflatable “front porch” where they’ll don “Astronaut Recovery Vests.”

Those will be used to hoist the astronauts onto HSC-23 helicopters and then delivered to the USS John P. Murtha, where they’ll undergo a checkup at a medical bay before getting transported back to Houston. Every part of the retrieval process has to go swimmingly to avoid any splashdown disasters.

The Orion craft, meanwhile, will be ferried to the ship via a floating dock. Once the module’s ashore, a truck will transport it to the Kennedy Space Center in Merritt Island, Florida.

Feeling spacey

Of course, following the mission, astronauts can experience of host of health effects due to the whiplash of returning to Earth after residing in microgravity for an extended period of time.

The change can throw astronauts’ inner-ear balance off kilter, as was the case with the crew of NASA’s SpaceX Crew-7 mission post-landing in 2024.

They reportedly struggled to walk with their eyes closed and then open — one of the first tests the crew completed upon touching back down on home soil. Crewmember Jasmin Moghbeli said her initial attempt at the fit-mus test resembled “a nice tap dance.”   

“I felt wobbly for the first two days,” she said. “My neck was very tired from holding up my head.”

Another side effect was extreme nausea, with some crew members reporting not being able to look down without feeling the spins.

NASA’s oldest active astronaut Don Pettit, 70, recalled feeling queasy after returning home in April 2025 after 220 days on the International Space Station. While descending, he recalled “emptying the contents of my stomach onto the steppes of Kazakhstan.”

Other side effects include everything from effects on the immune system, sleep disturbances and vision issues because microgravity causes blood to pool in the head, affecting the optic nerve, the BBC reported. The problem can begin after just two weeks in space.

Another aftershock? A loss of mass triggered by weightlessness in space.

After just two weeks, muscle mass can plummet by 20% while astronauts lose up to 2% of their bone density per month because their body no longer requires skeletal support in the microgravity environment.

The phenomenon is similar to how fish bones are thin because the animal is kept afloat in part by the buoyancy of water.

Adapting to life back on Earth

Thankfully, astronauts can combat space-related side effects by maintaining strict workout regimens on board.

To combat the atrophy, those stationed aboard the ISS engage in 2½ hours of daily exercises.

These include squats, deadlifts, rows and bench presses using a resistive exercise device, among other workouts.

Meanwhile, the Artemis II astronauts fought physical decline using the flywheel, a custom machine that they strap their feet into and pull on straps to trigger commensurate resistance, NPR reported.

Canadian astronaut Jeremy Hansen compared the yo-yo-like contraption to a rowing machine, claiming that you “row at a lower resistance and a fast pace” for a “cardiovascular workout.”

In most cases, equilibrium is restored within months of returning to the home planet.