The crew of the space mission Artemis II have returned to Earth after travelling 406,771 kilometres to the far side of the moon, the furthest any human has ventured into space so far.
Experts are working to understand the impact of such trips on the human body, as space missions become more frequent and longer — and the health risks involved go far beyond anything faced on Earth.
NASA has identified five hazards of spaceflight, including radiation, isolation and confinement, distance from Earth, gravity or the lack of it, and closed or hostile environments.
How does the body change in space?
The human body, it turns out, was not built for space.
Changes in gravity or the prolonged absence of it can erode bone density, redistribute brain fluid and impair heart function.
Even shifts between different gravity levels can trigger motion sickness and leave astronauts struggling to orient themselves.
According to recent NASA briefings, finding ways to improve human performance when dealing with these issues is a key priority for missions to the Moon and Mars.
Low gravity can also alter the heart and blood vessels, and the severity of it depends on the duration of the trip, increasing for longer missions.
Alterations to the cardiovascular system can lead to blood clots, heart arrhythmias and low blood pressure.
According to NASA, bones lose between 1% and 1.5% of their density each month during a four-to-six-month mission.
Meanwhile, long-term weightlessness can also cause shifts in the body fluids that may affect vision and intracranial pressure, known as spaceflight-associated neuro-ocular syndrome.
Changes in habits and schedules
In space, time and schedules do not function as they do down on Earth. Astronauts experience irregular light-dark cycles that can affect their sleep and circadian rhythms.
Those aboard the International Space Station, for instance, witness 16 sunrises and sunsets per day, which affects their sleep patterns.
Other changes to their daily routine relate to meals and the type of food available during a space mission.
Astronauts do not require the same amount or type of nutrients as they would need on Earth. Research from previous space missions has recorded instances in which crew members had an inadequate intake of energy, fluids, calcium and sodium.
Space nutrition therefore serves a dual role: providing astronauts with sufficient energy, while supplying the nutrients needed to counteract all the adverse effects of spaceflight.
NASA scientists work to ensure meals are acceptable, safe, nutritious, long-lasting, easy to prepare and varied enough to avoid menu fatigue.
A mental health challenge
Besides its physical toll, spaceflight also affects an astronaut's mood and mental health.
Isolation, confinement, distance from Earth and high stress can all increase the risk of anxiety, depression, and low morale.
Ongoing research about how crews can maintain psychological health is essential for the success and safety of future missions, NASA noted.
Measures that space agencies encourage to support mental health in space include keeping a journal, exercising daily, listening to music and writing to loved ones.
What happens if an astronaut falls ill in space?
Considering all these health risks, how does the crew manage sickness during a space mission?
NASA maintains that, regardless of mission length or objectives, all human spaceflight requires some degree of in-mission medical support.
However, to reduce the need for medical care during the mission, the agency focuses on preventive measures such as vitamin supplementation, full-body check-ups and a 14-day quarantine before the launch.
Based on the most commonly anticipated conditions, NASA tailors in-flight medical resources to ensure that the most likely or serious medical events can be managed effectively.
Most conditions can be treated similarly to Earth. However, treatment limitations mean that priority is given to medications that can serve multiple purposes and carry minimal side effects.
