NASA’s Expedition 73: Astronauts Study Brain, Balance, and Immunity on ISS

Astronauts on the International Space Station (ISS) are taking part in Expedition 73 to learn how weightlessness affects the human brain and body. NASA reports that “maintaining sense of balance and protecting immunity in space were the top human research experiments aboard the ISS” during recent crew activities. These studies examine how the brain and body adapt in microgravity – research that could help future space explorers and benefit health on Earth. As NASA prepares for future long-duration missions, understanding these biological changes is critical for keeping astronauts healthy on longer journeys in space.

Monitoring the Body for Long-Term Health

According to NASA, astronauts strap into harnesses and run on the station's treadmills — one crew member jogged on the Zvezda module's treadmill during a fitness check. They also use resistive exercise machines in the Tranquility module that simulate weightlifting to measure muscle and bone stress in space. These workouts help prevent the muscle and bone loss that can occur during long missions.

The crew regularly takes cognitive tests — a short computer quiz checks whether spaceflight is affecting reasoning, decision-making and visual tracking skills. They also practiced emergency procedures: one day the crew did cardiopulmonary resuscitation (CPR) drills, deployed medical kits and reviewed communication plans. These exercises help ensure the team stays prepared for any situation.

Tracking Brain and Immune System Changes

To study balance, flight engineers Jonny Kim and Zena Cardman worked in the station's Columbus lab to probe the vestibular system — the inner-ear and brain network that controls balance and spatial orientation. Cardman wore virtual-reality goggles displaying moving images while Kim ran the experiment computer.

This setup let the team see how Cardman perceives up and down without gravity. Such tests give researchers clues about how the brain adapts to life in orbit. Flight Engineer Kimiya Yui ran an Immunity Assay experiment, which checks if spaceflight changes cellular immunity. He collected stored blood and saliva samples, spun them in a space-lab centrifuge, and froze them for later analysis. Back on Earth, scientists will test these samples to see if long stays in orbit affect infection-fighting cells.