Astronauts traveling to the Moon, Mars,
and other future deep space destinations will likely make new and amazing
discoveries. Undertaking these exploration missions will not be possible
without increased risk to crew members from exposure to the space environment.
To reduce risks of the hazards of
spaceflight and protect astronauts from space
radiation, NASA is using the International Space Station to develop
capabilities to predict space radiation exposure for future exploration
missions.
Published in the journal Nature-Scientific
Reports, results from an ISS Medical Monitoring
study of International
Space Station astronauts
demonstrate how the sensitivity of an individual astronaut’s DNA to radiation
exposure on Earth can predict their DNA’s response during spaceflight as
measured by changes to their chromosomes.
“We wanted to know if it is possible to detect and
measure radiation exposure damage in the bodies of astronauts, and if there
were differences based on age, sex, and other factors that could be measured
before they go into space,” said senior scientist Honglu Wu from NASA’s Johnson
Space Center in Houston. “We hope to use these measurements to help develop and
compare methods of protecting astronauts from radiation.”
Space radiation originates from three primary sources:
particles trapped in the Earth’s magnetic field, particles shot into space
during solar flares, and galactic cosmic rays, which originate outside our
solar system. Exposure to radiation can increase the risk of developing cancer,
alterations to the central nervous system, cardiovascular disease, and other
adverse health effects. Life on Earth is protected from most space radiation by
the planet’s atmosphere and magnetic field.
On missions in low-Earth orbit, astronauts are also
protected from some of the space radiation exposure by a combination of Earth’s
magnetic field, spacecraft shielding, and limiting the astronaut’s time in
space. NASA’s Human Research Program seeks to conduct research in the field of
medical countermeasures such as pharmaceuticals and early disease detection
technology to help mitigate the consequences of space radiation exposure.
During exploration missions beyond Earth’s orbit, it may not be possible to
provide the same level of protection from shielding or limit mission exposure
time.
Space radiation is made
up of protons and all the elements on the periodic table. It enters the human
body at energies approaching the speed of light and can damage DNA. Credits:
NASA
As we prepare for these longer missions
and a permanent human presence in space, NASA’s Human Research Program seeks to
conduct research in the field of medical countermeasures such as
pharmaceuticals and early disease detection technology to help mitigate the
consequences of space radiation exposure. A key part of that is figuring out
ways to estimate the sensitivity of astronauts to radiation prior to flight and
continually assess long-term health for the remainder of their lifetimes.
As people age and live their lives, their chromosomes
accumulate alterations. These changes can result from normal bodily processes
or due to exposure to environmental factors. Chromosomes contain the DNA
building blocks of our bodies and altering them can increase the risk of
developing cancer and other diseases. During the ISS Medical Monitoring experiment, researchers studied blood samples from 43 space
station crew members to measure their levels of chromosome alterations from
radiation and other factors before and after a mission. These alterations to
chromosomes are observed in a very small percentage of individual cells within
a person’s blood.
The study involved three key measurements. Before
astronauts flew to the station, researchers examined their blood cells to
assess their baseline chromosomal status against which any future alterations
could be measured. Next, these blood samples were intentionally exposed to
gamma-ray radiation on Earth to measure how easily their cells accumulated
chromosomal changes. This measurement established each astronaut’s inherent
sensitivity to radiation. Finally, after the astronauts returned from their
missions, the study team again took blood samples from the individuals to
assess their level of chromosomal alterations.
Blood samples taken by former NASA astronaut Chris Cassidy before aboard the International Space Station. Samples like these were taken before and after astronaut’s missions to space to measure radiation damage of astronauts in space. Credits: NASA
Wu and retired NASA statistician Alan Feiveson then
compared each astronaut’s levels of post-flight alterations to their
corresponding background levels established before launching into space. In
addition, the investigators checked to see if any of this increase could also
be explained by age, sex, or individual sensitivity.
“It was an intriguing challenge to develop a
statistical method for analyzing all of the blood samples to see if an
astronaut’s pre-flight levels of radiosensitivity actually plays a role in
predicting their spaceflight-induced chromosome alterations,” said Feiveson.
After analyzing all of the data, the researchers found that, similar to
people on Earth:
- Older crew members had higher levels of baseline chromosomal
irregularities, and
- The blood cells of older astronauts were more sensitive to developing
chromosomal alterations compared to younger crew members.
These
results indicated that:
- Crew members with higher inherent sensitivity, as determined by gamma
radiation on the ground, were more likely to see higher levels of changes
to their chromosomes in their post-flight blood samples compared to those
with lower sensitivity.
- Individuals who showed higher baseline chromosomal alterations in
their pre-flight blood samples tended to also be more sensitive to
developing additional chromosomal changes compared to astronauts with low
baseline levels.
“The findings suggest that if older astronauts indeed have higher
sensitivities to radiation, they might be at higher risk of chromosome alterations,”
said Wu. “While experiencing chromosome alterations does not automatically mean
someone will develop cancer, it does raise the question of whether they are at
increased risk for it.”
Younger astronauts are thought to be more susceptible than older astronauts
to the long-term health consequences resulting from space radiation exposure.
This is partly because younger astronauts have more lifespan remaining and
could live long enough to develop a cancer from the radiation exposure; it
usually takes five to 20 years or more after the radiation exposure for cancer
to occur.
“When thinking about going to Mars, we typically have thought it might be better to send older astronauts because of their experience and lower risk of developing cancer in their lifetime,” said Wu. “Now, based on this new research, we know that we should study the age effects of radiation exposure more.”
While people protect
their eyes from the sun’s radiation during a solar eclipse, NASA’s Human
Research Program (HRP) is working to protect the whole human body from
radiation in space. Space radiation is dangerous and one of the primary health
risks for astronauts. Credits: NASA
For more information on how NASA is addressing the hazard of space
radiation, visit the Human Research Program’s space radiation information
webpage.
For daily updates, follow @ISS_Research, Space Station Research and Technology News or our Facebook. For opportunities
to see the space station pass over your town, check out Spot the Station.
Charlie Plain International Space Station Program Research Office Johnson Space Center
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