On April 10, 2026, as the world watched with bated breath, the Artemis II crew began their final approach toward Earth, closing out a mission that has already been called historic by experts and space enthusiasts alike. Astronauts Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen have just completed a record-breaking journey to the far side of the moon, traveling an astonishing 252,756 miles from their home planet—farther than any human has ever ventured before, according to Sky News.
For NASA, Artemis II isn’t just another notch on the agency’s belt; it’s a crucial step in a long-term vision that stretches beyond lunar horizons to the red sands of Mars. The mission, which lasted approximately 10 days, is being hailed as a proving ground for the future of deep space exploration. Yet, as dazzling as the technical achievements are, the mission also brings to the fore a less visible, but equally critical, set of challenges: the health and well-being of astronauts in the harsh environment of space.
Humans have spent millions of years evolving to thrive on Earth, a planet with gravity, sunlight, and a protective atmosphere. Take those away, and the body starts to protest. So, what exactly does space do to the human body—and how is NASA tackling these issues as it prepares for even longer journeys?
One of the most pressing concerns is space radiation. Unlike on Earth, where the atmosphere and magnetic field shield us from harmful cosmic rays, deep space offers little protection. Dr. Haig Aintablian, director of space medicine at UCLA, explained to Sky News, "Once you go beyond low Earth orbit, you lose much of the protection of Earth's magnetic field." He called radiation one of the "real challenges" posed by deep space. The risks aren’t trivial: exposure can lead to DNA damage, increased cancer risk, neurodegenerative effects, cardiovascular issues, and even immune system problems.
While the International Space Station (ISS) orbits about 250 miles above the Earth—still within the relative safety of the planet’s magnetosphere—Artemis II’s journey took the crew far beyond this protective bubble. The further astronauts venture, the more radiation they encounter, making missions like Artemis II a critical testbed for future, longer-term deep space travel.
But radiation is just one piece of the puzzle. The absence of gravity—what scientists call microgravity—also wreaks havoc on the human body. Floating around in zero gravity may look like fun (and, sure, it probably is for a while), but gravity plays a vital role in regulating everything from our inner ear balance to how our bones and muscles function. Dr. Aintablian noted, "The body is built to live and work in gravity. When that gravity signal is removed, the inner ear has to recalibrate, muscles and bones are used differently, and fluids shift upward toward the head. That is why we can see changes in balance, strength and, in some cases, vision."
One of the most serious side effects is bone density loss. NASA estimates that astronauts can lose about 1% of their weight-bearing bone mass for every month spent in space if precautions aren’t taken. This means bones become weaker and more brittle—a worrying prospect for anyone planning a long stay on the moon or a trip to Mars. Muscle atrophy, or the thinning and weakening of muscle tissue, is another common issue.
Then there are the headaches. According to a study published in 2024 and cited by Sky News, 22 out of 24 astronauts who spent up to 26 weeks in space reported frequent headaches. Other symptoms include motion sickness, dizziness, cardiovascular conditioning problems, and disrupted sleep patterns. While many of these effects are temporary and improve after returning to Earth, some—particularly those involving vision or bone health—can linger much longer.
So how does NASA deal with this daunting list of health risks? The answer is a combination of high-tech monitoring, careful planning, and a healthy dose of old-fashioned vigilance. Each astronaut is assigned a flight surgeon, essentially a personal doctor who monitors their health before, during, and after the mission. Dr. Aintablian explained, "On a mission like Artemis II, doctors are tracking not just how the crew feels, but how their bodies are responding in real time."
The toolkit is extensive. There’s radiation monitoring, sleep and activity tracking, exercise countermeasures (think specialized gym equipment designed for zero gravity), and a structured post-landing recovery plan. After the mission, astronauts undergo a battery of tests—bloodwork, balance and vestibular assessments, strength and cardiovascular checks, sleep monitoring, and behavioral health evaluations. "There are a broad set of checks, including blood and other biological samples, balance and vestibular testing, strength and cardiovascular assessments, sleep monitoring, and behavioural health evaluations," Dr. Aintablian told Sky News.
Why all this scrutiny? The data collected from Artemis II isn’t just about keeping these four astronauts healthy—it’s about paving the way for future crews who will venture even further from home. "Artemis II is a critical step because it gives us human data from beyond low Earth orbit. That is essential if we are going to prepare crews safely for longer lunar missions and, eventually, Mars," Dr. Aintablian emphasized.
The Artemis II mission is also a reminder that, despite all our technological prowess, space remains an unforgiving frontier. Each mission brings new lessons, not just in engineering and science, but in understanding the limits—and the resilience—of the human body. As the four astronauts prepare to splash down in the Pacific Ocean at about 1am UK time on April 11, 2026, their journey will be remembered not just for its records, but for the groundwork it lays for humanity’s next giant leap.
For now, the world watches and waits, marveling at the courage and adaptability of those who dare to leave Earth behind. The Artemis II crew’s journey is a testament to human ingenuity and determination, offering a glimpse of the challenges—and the extraordinary possibilities—that lie ahead as we set our sights on the stars.