Astronaut in Outer Space

Is it safe for humans to fly into space? ISS experiments show risks for future space flights

Astronauts can be exposed to high-energy charged particles from galactic cosmic rays and solar particle events, as well as secondary protons and neutrons after leaving Earth’s protective atmosphere. Since biomolecules, cells and tissue have different ionization patterns than terrestrial radiation, the associated biological consequences are hardly known and the extent of the associated risk is subject to enormous uncertainties.

The mouse cell study analyzed the effects of space radiation and will help scientists better assess the safety and dangers of space travel.

An international team of scientists conducted a long-term experiment aboard the International Space Station to study the effects of cosmic radiation on mouse embryonic stem cells. Her research will help scientists more accurately assess the risks and safety of space radiation for future human spaceflight.

The team recently published their findings in the journal helioon.

The researchers performed a direct quantitative assessment of the biological effects of space radiation in their study by transporting frozen mouse embryonic stem cells from Earth to the International Space Station, exposing them to space radiation for four years, and quantifying the biological effect by evaluating chromosomal aberrations. The results of their experiment show for the first time that the biological effects of space radiation are in close agreement with previous predictions derived from the physical measurement of space radiation.

Sketch of the space experiment “Stem Cells”.

Frozen mouse embryonic stem cells were shot from the ground to the International Space Station, stored for a long period of time, recovered on the ground and examined for chromosomal aberrations. Photo credit: Takashi Morita, OMU

Now that normal humans can travel into space, the likelihood of lengthy human missions to distant planets like the moon and

Mars is the second smallest planet in our solar system and the fourth planet from the sun. It’s a dusty, cold desert world with a very thin atmosphere. Iron oxide is widespread on the surface of Mars, leading to its reddish color and nickname "The Red Planet." The name Mars comes from the Roman god of war.

” data-gt-translate-attributes=”[{” attribute=””>Mars is growing. However, space radiation continues to be a barrier to human exploration. In-depth research has been done by scientists to measure the physical doses of space radiation and better understand how it affects the human body. However, since most previous studies were done on the ground rather than in space, the findings were subject to uncertainty, given that space radiation consists of many different types of particles with varying energies and astronauts are continually irradiated at low dosage rates. On Earth, the space environment cannot be precisely reproduced.

“Our study aims to address the shortcomings of previous ground-based experiments by performing a direct quantitative measurement of the biological effect of space radiation on the International Space Station and comparing this real biological effect with physical estimates in the ground-based experiments,” said Takashi Morita, a professor at the Graduate School of Medicine, Osaka Metropolitan University. “The findings contribute to reducing uncertainties in risk assessments of human space flights.”

The team prepared about 1,500 cryotubes containing highly radio-sensitized mouse embryonic stem cells and sent them to space. Their study was complex in its scope, with seven years of work before launch, four years of work after launch, and five years for analysis. “It was difficult to prepare the experiment and to interpret the results, but we successfully obtained quantitative results related to space radiation, meeting our original objective,” said Professor Morita.

Looking ahead, the researchers hope to take their studies a step further. “For future work, we are considering using human embryonic stem cells rather than mouse embryonic stem cells given that the human cells are much better suited for human risk assessment, and it is easier to analyze chromosome aberrations,” said Professor Morita.

Future studies might also include launching individual mice or other experimental animals to analyze their chromosome aberrations in space. “Such experiments in deep space can further contribute to reducing uncertainties in risk assessments of prolonged human journeys and stays in space,” concluded Professor Morita.

Reference: “Comparison of biological measurement and physical estimates of space radiation in the International Space Station” by Kayo Yoshida, Megumi Hada, Akane Kizu, Kohei Kitada, Kiyomi Eguchi-Kasai, Toshiaki Kokubo, Takeshi Teramura, Sachiko Yano, Hiromi Hashizume Suzuki, Hitomi Watanabe, Gen Kondoh, Aiko Nagamatsu, Premkumar Saganti, Francis A. Cucinotta and Takashi Morita, 17 August 2022, Heliyon.
DOI: 10.1016/j.heliyon.2022.e10266

The study was funded by the Japan Aerospace Exploration Agency, the Japan Space Forum, and the Ministry of Education, Culture, Sports, Science, and Technology of Japan. 

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