If the Artemis II mission to the moon is to be a step toward sustained human exploration, even to Mars, then one of its contributions must be helping scientists figure out how to keep astronauts safe when they are days, or even months, away from Earth.
Consider that in January, while aboard the International Space Station, NASA astronaut Michael Fincke suddenly found himself unable to speak for about 20 minutes. Despite a heart attack and choking being ruled out, NASA ended the mission early to bring Fincke home for evaluation, the first time a medical concern ever required an astronaut to leave a space station early.
The crew wore sensors that continuously tracked their hydration, breathing, cardiovascular performance and radiation exposure.
If that were to happen on a future Mars mission, then the return to Earth could take years. Thus, the trend in space medicine has been toward advancing capabilities to diagnose and treat astronauts independently in space rather than relying on a return home. And we can count on our scientists studying the data recorded and sent back by our astronauts who are scheduled to splash down in the Pacific Ocean on Friday evening.Â
During the lunar missions of the 1960s, doctors monitored astronauts mainly with heart rate telemetry and limited metabolic data. But the crew of Artemis II wore sensors that continuously tracked their hydration, breathing, cardiovascular performance and radiation exposure. Portable ultrasound machines allowed crew members to evaluate cardiovascular function and internal organs even without a physician physically present.
Indeed, what has made Artemis II particularly exciting from a medical standpoint was the sheer breadth of human research conducted. NASA packed the roughly 10-day flight with studies that spanned nearly every major system in the body. An immune biomarkers investigation tracked how deep space conditions affected stress hormones, immune cells, and dormant viruses through blood and saliva samples, with crew members blotting saliva onto special paper booklets since refrigeration was not an option in Orion’s tight quarters.
Wrist-worn devices monitored sleep, activity and behavioral performance in real time, giving flight controllers and researchers a window into how crew well-being holds up under the stress of deep space confinement.Â
Modern astronaut health care has improved dramatically since the Apollo era.
Long-duration missions on the ISS had already helped scientists better understand how the human body changes in space. Without gravity, bones weakened at rates of about 1%–1.5% per month, and muscles, especially postural muscles, shrank unless astronauts exercised daily. Data collected from those missions indicated that cardiovascular system adapted to microgravity as well, with reduced blood plasma volume and changes in heart function that could make standing difficult for astronauts returning to Earth.
One of the most surprising discoveries from spaceflight research has been a condition called spaceflight-associated neuro-ocular syndrome. Astronauts can develop swelling of the optic nerve and subtle changes in vision caused by fluid shifting toward the head in microgravity. Although most symptoms improved after the astronauts returned to Earth, researchers are still studying how these changes might affect longer missions to the moon or Mars.
Radiation exposure is another concern when traveling deeper into space. The ISS remains partly protected by Earth’s magnetic field, but astronauts traveling to the moon and Mars face higher exposure to cosmic radiation, especially from higher energy particles. One of the goals of Artemis II, then, was to help scientists measure these risks more precisely and test protective strategies for future missions.
Artemis I flew with over 5,600 radiation sensors, confirming Orion’s shielding could protect a crew. Artemis II took it further, however. Each astronaut carried a personal dosimeter, six active sensors called Hybrid Electronic Radiation Assessors were positioned throughout the cabin and an upgraded German built M-42 EXT monitor with six times the resolution of its Artemis I predecessor measured exposure from heavy ions, considered among the most biologically dangerous forms of cosmic radiation.
Perhaps the most fascinating experiment was AVATAR, or A Virtual Astronaut Tissue Analog Response. Organ-on-a-chip devices, roughly the size of a USB drive, contained living bone marrow tissue grown from the actual crew members’ cells. These chips flew the same trajectory as the astronauts and were exposed to the same deep space radiation and microgravity. Bone marrow was chosen because it produces red blood cells, white blood cells and platelets, making it ideal for understanding how radiation disrupts blood cell formation and immune function. When the chips are back on Earth, researchers will perform single-cell RNA sequencing to measure how thousands of genes changed within individual cells during the flight. The implications extend well beyond spaceflight, as understanding how radiation damages bone marrow at the cellular level could reshape how we approach radiation therapy, chemotherapy and personalized medicine on Earth.
Studies have shown that some astronauts experienced changes in immune response and reactivation of dormant viruses during long missions. Additionally, the microbes inside the spacecraft also adapted and evolved to the spaceflight environment. Sleep disruption and isolation could further affect mood, concentration and decision-making, leading to worsening effects from psychological stress.
It’s not all glamour. The people we’ve flown into space have experienced significant changes to their bodies.
It’s not all glamour, then. The people we’ve flown into space have experienced significant changes to their bodies, and if we are to continue space exploration, then we need to understand those changes and how to mitigate them as thoroughly as possible.
Many of the medical and research capabilities present on the Artemis II mission were not available when humans last visited the moon in 1972. The data collected during this mission, then, represented a more comprehensive view into how humans could explore and adapt to the rigors of spaceflight to our planetary neighbors. Artemis II was an important step toward preparing crews to manage risks independently, bringing humanity closer to spending more time outside Earth’s orbit.
Dr. Owais Durrani
Dr. Owais Durrani is an emergency medicine physician in Houston. Dr. Durrani has a background in political science and works to advocate for eliminating health inequities.
Dr. Alaina Rajagopal, M.D., Ph.D CTropMed FAWM, is an emergency medicine physician, inventor, and entrepreneur who is focused on improving the practice of medicine in remote locations.
Robert Glatter, M.D., is assistant professor of emergency medicine at Lenox Hill Hospital, Zucker School of Medicine at Hofstra/Northwell, Northwell Health. He has a keen interest in medical aspects of space travel, along with global health and public health policy.
