NASA's Human Research Program has been unfolding answers to how the human body reacts to being in space, for over a decade.

The various studies, conducted by the space agency under its HRP division, have suggested that space is an unfriendly and dangerous place for mankind and a stint there has adverse implications on the body.

Impact On Brain

Researchers have noticed visible changes in the brains of astronauts returning from the International Space Station.

A study published on Nov. 2 in The New England Journal of Medicine found that the brain scan of 27 crew members showed increases and decreases in the volume of gray matter in the different parts of the brain, which was in tandem with the duration of time spent in space.

The research, conducted by a NASA-funded team of radiologists, analyzed the brain MRIs of 34 astronauts both before and after their space trip. The scientists found that many of the astronauts' brains had become repositioned inside their skulls, floating higher than before, upon returning to Earth.

The space between certain areas in the brains also seemed to have shrunk. The changes were more pronounced in the astronauts that had spent more time in space.

"We know these long-duration flights take a big toll on the astronauts and cosmonauts; however, we don't know if the adverse effects on the body continue to progress or if they stabilize after some time in space," neuroradiologist at the Medical University of South Carolina and study author Dr. Donna Roberts said.

"These are the questions that we are interested in addressing, especially what happens to the human brain and brain function," Roberts added.

Visual Impairment

Last year in November, researchers had presented a paper at the annual meeting of the Radiological Society of North America that suggested that space missions could have an adverse effect on the eyesight of astronauts.

Astronauts who spend a long time in space suffer from what is known as visual impairment intracranial pressure, according to the paper. The syndrome, which leads to a blurry vision, is caused due to the volume changes in the clear fluid around the spinal cord and the brain.

Space Travel Alters Gene Expression

A research carried out by NASA, based on the Twins Study that focused on four categories of research split into 10 investigations to evaluate identical twin astronauts Mark and Scott Kelly, has shown that space travel can change gene expression the moment the human body gets into space.

The research has suggested that space mission increases methylation, which is the process of the genes turning on and off. The effect can be seen as soon as astronauts get into space, just like fireworks.

Effects Related To Interplanetary Travel

There are other risks and effects that could also be associated with longer space missions, such as a crewed Mars mission in the future, according to NASA's study of the human body in space as a part of the space agency's ongoing Human Research Program.

The research has suggested that transitioning back to the gravity of Earth from Mars can impact the body's locomotion, balance, head-eye and hand-eye coordination, spatial orientation, and motion sickness.

The study found that the bone loses minerals and its density drops over one percent every month without gravity working on the body, which could lead to more chances of osteoporosis-linked fractures in later life. A person also becomes prone to developing kidney stones because of dehydration and increased calcium excretion from the bones.

Interplanetary travel also means astronauts are exposed to a number of radiation sources, including radiation trapped in the Van Allen belts, galactic cosmic rays, solar particle events, and ionizing radiation. High atomic number and energy ions can cause damage to DNA and tissues.

Cardiovascular risk is also acute among space travelers due to weightlessness caused to the arterial vasculature and direct impact of space radiation, as per NASA's Human Research Program study.

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